Derivation of specific name
Bromus inermis, smooth brome, is a leafy, sod-forming, perennial, cool season grass that spreads by rhizomes. This species is both native and introduced. The stems vary in height from 2 to 4 feet. The plant produces numerous basal and stem leaves that vary in length from 4 to 10 inches. Frequently the leaves are marked by a transverse wrinkle resembling a “W” a short distance below the tip. The flower head develops a characteristic rich purplish-brown color when mature. The seed is produced in semi-compact 5 inch long panicles with ascending branches. The flat compressed seed is usually awnless, about 1/3 inch long, and smooth. There are approximately 136,000 seeds per pound. Smooth brome is the most widely used of the cultivated bromegrasses and has been cultivated in the U.S. since the early 1880s.
bromegrass, Austrian brome, Hungarian brome, Russian brome
Regularity: Regularly occurring
Regularity: Regularly occurring
Range and Habitat in Illinois
Global Range: Bromus inermis Leyss. is a Eurasian species ranging from France to Siberia, apparently introduced in the United States by the California Experiment Station in 1884 (Kennedy 1899, Archer and Branch 1953).
Within the United States smooth brome has been introduced in the northeastern and northern Great Plains states as far south as Tennessee, New Mexico and California. It has become naturalized from the maritime provinces to the Pacific coast north to Alaska to California and through the plains states.
Occurrence in North America
KS KY ME MD MA MI MN MO MT NE
NV NH NJ NM NY NC ND OH OK OR
PA RI TN TX UT VT WA WV WI WY
DC AB BC MB NB NF NT NS ON PE
PQ SK YT
Alaska and all the Canadian provinces and territories south to southern
California and New Mexico, northern Oklahoma, and North Carolina
Regional Distribution in the Western United States
This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):
1 Northern Pacific Border
2 Cascade Mountains
3 Southern Pacific Border
4 Sierra Mountains
5 Columbia Plateau
6 Upper Basin and Range
7 Lower Basin and Range
8 Northern Rocky Mountains
9 Middle Rocky Mountains
10 Wyoming Basin
11 Southern Rocky Mountains
12 Colorado Plateau
13 Rocky Mountain Piedmont
14 Great Plains
15 Black Hills Uplift
16 Upper Missouri Basin and Broken Lands
Distribution in Egypt
Native over much of Europe and temperate Asia.
Distribution and adaptation
Smooth brome is best adapted to cooler climates and is generally hardier than tall fescue or orchardgrass. It is resistant to drought and extremes in temperature. This plant is very susceptible to disease in areas of high humidity. Smooth brome grows best on slightly acid to slightly alkaline well drained clay loam soils with high fertility but it will also grow well on lighter textured soils where adequate moisture and fertility are maintained. Smooth brome performs best in a pH range of 6.0 to 7.5. Stands are difficult to obtain and growth is poor on soils high in soluble salts.
Smooth brome is distributed throughout most of the United States. For a current distribution map, please consult the Plant Profile page for this species on the PLANTS Website.
Smooth brome is an exotic, cool-season grass from 1.3 to 3.2 feet
(0.4-1.0 m) tall. Blades are flat. The inflorescence is an open
panicle from 2.4 to 6.8 inches (6-17 cm) long bearing 6 to 11-flowered
spikelets. Lemmas have short awns ( less than 2 mm) or are unawned [53,54,61].
Two principle types of smooth brome are recognized, the northern and
southern. The northern type is weakly rhizomatous, with leaves well up
on the stem and short glumes. A few northern cultivars are actually
bunchgrasses. The southern type is strongly rhizomatous, with leaves
near the base of the stem and long glumes. Other notable differences
are earlier spring growth of the southern type and more even growth of
the northern type through the growing season .
In a meadow in West Virginia on shallow silty loam, smooth brome roots
grew to a depth of 18 inches (46 cm), with most of the root biomass
occurring in the first 3 inches (7.6) of soil. (Average root
productivity was 717.7 lbs/acre inch at 0-3 inches below ground .)
Witte  found roots as long as 9.4 feet (2.87 m).
Due to cloning, smooth brome is a long-lived species. Plantings have
persisted for at least 60 years .
The ascending or stiff branches of the open panicle are a key characteristic distinguishing Bromus inermis and Bromus erectus from a group of similar native bromegrasses. The awnless lemmas, from which the species derives its Latin name, distinguish Bromus inermis from both the introduced and similar Bromus erectus and from the native Bromus pumpellianus.
Catalog Number: US 3168443
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Card file verified by examination of alleged type specimen
Preparation: Pressed specimen
Collector(s): B. Brues
Year Collected: 1904
Locality: Milwaukee, McKinley Park, along shores of Lake Michigan., Wisconsin, United States, North America
- Type fragment: Brues, B. B. 1911. Trans. Wisconsin Acad. Sci. 17: 73.
Range and Habitat in Illinois
Comments: In its native range smooth brome grows on roadsides, riverbanks, edges of fields and woods and pastures. Bromus inermis was first recognized as a potential forage grass in Europe because of its drought resistance (Kennedy 1899).
Within the United States a variety of agricultural strains have been developed from two natural strains, a "northern" and a "southern" strain. The southern strain is more tolerant of drought and heat than the northern strain (Newell and Keim 1943).
Greenhouse and field tests in Wisconsin suggest that smooth brome has better root growth in sandy than in silty soils (Lamba et al. 1949). Artificial aeration of silt loam produced better root growth than in unaerated soils (Lamba et al. 1949). Smooth brome has a high mortality rate on organic soils (Myhr et al. 1966). The possible relationship between poor soil aeration and mortality has not been investigated. Tolerance of smooth brome to spring flooding is estimated at 24 days (Seamands 1979). Salt tolerance is considered "moderate" (Seamands 1979). The sun-loving habit of smooth brome is substantiated by research showing that seed production, numbers of shoots and rhizomes, and dry weight of all plant parts are reduced by shade (Watkins 1946, Dibbern 1947).
Smooth brome is widely adapted to a variety of sites. It is common in
riparian zones, valley bottoms, and dryland sites. [48,56,119]. It is
adapted to all soil textures [49,55,90], although it may not thrive on
sand or heavy clay . Smooth brome tolerates acid soils; it
comprised the dominant cover on a coal spoil of pH 4.5 in British
Columbia . It does not grow on soils that are more than moderately
alkaline . It is fairly saline tolerant . Smooth brome grows
best on moist, well-drained soils , but tolerates poorly drained
soils . Smooth brome is best adapted to regions receiving more than
15 inches (380 mm) of annual precipitation [98,119]. Eleven inches (280
mm) of annual precipitation is the minimum that will support smooth
brome without irrigation .
Some cultivars of smooth brome are adapted to northern latitudes and
high elevations [60,102]. Smooth brome persists to about 9,000 feet
(2,743 m) elevation in the northern Rocky Mountains [24,119] and to
about 11,000 feet (3,300 m) in the central and southern Rocky Mountains
. General elevational ranges in several states are:
from 7,000 to 10,000 feet (2,134-3,048 m) in Arizona 
below 8,900 feet (2,700 m) in California 
from 4,500 to 10,000 feet (1,372-3,048 m) in Colorado 
from 4,096 to 10,352 feet (1,280-3,235 m) in Utah 
Habitat: Rangeland Cover Types
This species is known to occur in association with the following Rangeland Cover Types (as classified by the Society for Range Management, SRM):
More info for the term: cover
Smooth brome occurs in most SRM Cover Types.
Habitat: Cover Types
This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):
More info for the term: cover
Smooth brome occurs in most SAF Cover Types.
This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):
Smooth brome occurs in most FRES ecosystems.
Introduced agricultural weed.
A clean firm seedbed is needed. Due to the slow germination and establishment of smooth brome, spring seedings are especially preferred in the northern states. In southern areas, late summer seedings are a second option. Fall seedings should be made at least 6 weeks before a killing frost is expected. Seeding rates are typically 5-10 pounds per acre in mixtures, and about 15 pounds when seeded alone. When smooth brome is seeded in a mixture with alfalfa, the alternate row method will give the best results. For seed production plantings under irrigation, seed in rows 30 to 42 inches apart at a rate of 3 to 4 pounds per acre. Seedings should be drilled at a depth of 1/2 to 3/4 inch. If broadcast increase the seeding rate and cultipack after planting.
Fire Management Considerations
If smooth brome is growing in association with a legume and an
increase in smooth brome productivity is desired, early spring rather
than late summer or early fall fire is generally recommended.
Late-season fire harms many legume species [62,74,94].
Fire control: An important management goal in remnant prairie is to
maintain or increase diversity of native species and depress growth and
production of exotic invaders such as smooth brome. Becker 
concluded that annual spring burning on Pipestone National Monument
prairie helped control smooth brome and other cool-season exotic
grasses, and that the structure, composition, and diversity of the
severely degraded native prairie was improved by annual burning.
Similarly, two consecutive spring fires on portions of an eastern South
Dakota tallgrass prairie where smooth brome was dominant reduced smooth
brome and Kentucky bluegrass coverage .
Blankespoor and Larson's  prescribed fire-water treatment study
suggests that prescribed late spring fire will most effectively control
smooth brome in wet years. They recommend continuing a program of
prescribed burning through drier years, however. Since they found that
smooth brome increased in importance without burning, and that increases
were greatest when initial smooth brome biomass was low, they concluded
that failing to burn smooth brome in dry years is likely to accelerate
For control, Willson  recommended burning smooth brome in late
spring after it has produced five or more green leaves per tiller;
unelongated tillers, which are not greatly damaged by fire, generally
have fewer than five green leaves per tiller.
Postfire plantings: Smooth brome has been extensively planted to
increase forage and/or reduce erosion in burned areas
[14,29,34,35,61,79,106]. This practice has been questioned because
native species appear to be at least equally effective in reducing
erosion, and exotic grasses such as smooth brome may interfere with the
growth of native forbs and grasses .
Postfire plantings of smooth brome have been successful across a wide
range of habitats and climates. For example, big sagebrush-threetip
sagebrush (Artemisia tridentata-A. tripartita) rangeland in Idaho was
burned in summer 1937 and seeded with one of six grasses to reduce
sagebrush cover and increase forage production. On plots seeded to
smooth brome, smooth brome yield increased from 57 pounds per acre in
1940 to 148 pounds per acre in 1948. Sagebrush coverage was lower on
smooth brome plots than on plots of any of the five other grasses
In Montana smooth brome seeded in after stand-replacing fire in
lodgepole pine (Pinus contorta) showed "fair" vigor (density of 4.4
plants/sq ft) on slopes with a southwestern exposure and "good" vigor
(density of 8.2 plants/sq ft) on slopes with a northeastern exposure
Litter accumulation: Bleak  reported a 39 percent average rate of
decay of bagged smooth brome litter in direct contact with snow cover
over two consecutive winters.
Broad-scale Impacts of Plant Response to Fire
Late spring burning has sometimes been only marginally effective in
controlling smooth brome [23,93]. Kirsh  reported that smooth brome
was actually stimulated by an early May prescribed fire. This variable
response may be due, in part, to the fact that control effects have been
targeted against several cool-season exotic grasses rather than smooth
brome alone. Since phenologies of cool-season grasses differ, timing of
a particular fire may reduce other cool-season species but not smooth
In a defoliation experiment, Harrison and Romo  found that smooth
brome regrowth was related to both growth stage and soil moisture
conditions. After defoliation in the vegetative stage, smooth brome
resumed growth in 45 to 75 growing days when soil moisture was
favorable. Smooth brome did not resume growth until the next growing
season after clipping in dry years. When plants were defoliated during
reproduction, new tillers did not emerge until the next fall regardless
of soil moisture conditions.
Blankenspoor and Larson  used a prescribed fire and watering
treatment to determine smooth brome's response to late spring (9 May,
1989) fire under low and high soil moisture levels. They found the
following changes in percent smooth brome biomass after treatment:
high-water -17.0 +10.5
low-water -8.2 +11.7
Decreases in the two burned treatments were significantly different
(p=0.05), but increases in the unburned treatments were not. Apparently
when soil moisture is high, warm-season grasses are able to outcompete
fire-injured smooth brome for water. With less soil moisture available,
warm-season grasses may be less able to take competitive advantage of
fire-injured smooth brome .
In the same study, Blankespoor and Larson  found that on unburned
plots, increases in smooth brome biomass were greatest on plots with low
initial smooth brome biomass. This relationship approached significance
(p=0.06) for unburned, high-water plots and was strongly significant
(p=0.001) for unburned, low-water plots. As a cool-season species with
substantial growth occurring early in the growing season, smooth brome
apparently encounters little competition from water-stressed,
warm-season plants in the absence of fire.
Lyon's Research Paper (Lyon 1971) provides further information on
prescribed fire use and postfire response of plant species including
Plant Response to Fire
Early spring (late March-April) or late-season (late summer-fall) fire
can increase smooth brome productivity [62,65], especially when smooth
brome has become sod-bound. Late spring fire generally damages
cool-season grasses such as smooth brome [8,82]. Old , Kirsch and
Kruse , and Blankespoor  have reported reductions in smooth
brome with late spring burning.
Old  attributed decreases in smooth brome after late April fire to
the advanced stage of development of smooth brome. Rate of smooth brome
regrowth after fire cannot always be predicted based solely upon season
of burning and attendant phenological stage, however. Blankenspoor and
Larson  cited soil moisture and nutrient levels and soil texture as
factors other than phenological stage that may affect smooth brome rate
In order to determine at which stage of growth smooth brome is most
susceptible to fire, Willson  prescribe-burned smooth brome at
tiller emergence (late March at the Mead, Nebraska, study site), tiller
elongation (mid-May), and heading (late May). Late March fire had no
significant effect on smooth brome. Mid-May or late May fire reduced
fall tiller density approximately 50 percent when compared to controls.
Examples of late spring fire: Short- and mid-grass prairie of Pipestone
National Monument, Minnesota, was spring-burned (mid- to late April)
annually from 1983 to 1987. The prairie had been severely degraded by
invasion of cool-season exotic grasses including smooth brome,
quackgrass (Elytrigia repens), and Kentucky bluegrass. Fire severity
was low to moderate except in 1984, when high fuel levels were present.
Smooth brome postfire coverage was :
1984 1985 1987
---- ---- ----
season spring spring summer
cover (%) 21.3 22.4 26.4(a)
a = data pooled with quackgrass
Lack of flower and seed production was noted in the cool-season grasses
including smooth brome, while native warm-season grasses increased
height growth and seed production. Height (cm) of smooth brome was
as follows :
1983 1984 1985 1987
--------------- --------------- ------ ------
spring summer spring summer spring summer
60 50 60 60 50 40
Smooth brome flowering was inhibited by a 2 May, 1972, prescribed fire in
Minnesota prairie .
Examples of fire in seasons other than late spring: On the Rathbun
Wildlife Area in southern Iowa, smooth brome is managed as ring-necked
pheasant cover. Smooth brome showed a significant (P less than 0.05) increase in
percent coverage following September or April prescribed burning.
February burning resulted in a nonsignificant decrease in smooth brome
coverage, with significant declines in smooth brome frequency in some
A 22 April, 1983, prescribed fire on the Hillendale Game Farm of central
Pennsylvania increased smooth brome production. On 5 October, 1983,
production was 69 kilograms per hectare on the unburned control and 612
kilograms per hectare on the burn .
In Iowa, three consecutive early spring (23-28 March, 1986; 11-12 April,
1987; 13-20 April, 1988) prescribed fires in pastureland excluded from
grazing had no significant effect on smooth brome. On some plots,
atrazine was applied 7 to 10 days after burning; the fire plus atrazine
treatments had no significant effect on smooth brome .
Immediate Effect of Fire
Most smooth brome cultivars are rhizomatous [56,110], and survive fire
by sprouting from rhizomes. Weakly rhizomatous or bunchgrass types
probably regenerate after fire primarily by tillering. Rates of
postfire recovery probably differ between cultivars, with rhizomatous
types recovering more quickly than bunchgrass types, but such
differences have not been documented in the literature.
Periodic early spring or fall fire promotes rhizomatous smooth brome by
removing litter from sod-bound plants [56,110].
More info for the terms: cover, shrubs
Smooth brome generally invades after disturbance and persists
[19,20,37]. It is a common invader of disturbed prairie throughout the
Great Plains [112,125,126]. In Yellowstone National Park, Wyoming,
smooth brome cover was similar in young eastern cottonwood (Populus
deltoides), mature eastern cottonwood, and grassland areas . Boggs
and Weaver  reported that along the Yellowstone River, moderate
grazing increased the occurrence of shrubs in mature eastern cottonwood,
and severe grazing converted the area to smooth brome, timothy (Phleum
pratense), and Kentucky bluegrass (Poa pratensis).
Smooth brome tolerates moderate shade to full sun [49,56]
Smooth brome reproduces by seed, rhizomes, and tillers. Spread by seed
has been rated moderate, and vegetative spread has been rated good .
Smooth brome is usually cross-pollinated [72,86], although it may
self-fertilize from different spikelets of the same plant . McKone
 found that seed set was significantly lower in smooth brome than in
other brome species. Insect herbivory has been cited as a factor
reducing seed set in smooth brome [86,91]. Seed yield of smooth brome
broadcast-planted in Michigan 174 pounds per acre when grown with
alfalfa and 121 pounds per acre when grown alone . Seed has
remained viable for 22 months to over 14 years [49,55]. Seed stored in
a shed for 19 years showed 20 percent germination . Seed requires
stratification to germinate. Germinative capacity of fresh, stratified
seed has varied from 83 to above 95 percent in the laboratory .
Optimal temperatures for germination in the greenhouse were from 68 to
86 degrees Fahrenheit (20-30 deg C) . Like all cool-season species,
however, smooth brome can germinate at lower temperatures. Bleak 
reported that smooth brome seed sown in late fall to early winter in
central Utah germinated and produced roots and shoots under deep snow
cover. Light enhances germination but is not required .
Seedling growth is rapid [56,59]. Knobloch , who described
germination and seedling development in detail, reported that 54 days
after sowing, greenhouse-grown seedlings had 150-millimeter-long roots,
five leaves, and had begun tillering. Baker and Jung  found that
under greenhouse conditions, the optimal day temperature for growth was
between 64.9 and 76.8 degrees Fahrenheit (18.3-24.9 deg C), and that food
reserves were depleted less with low night temperatures than with warm
night temperatures. Cultivars differ in rate of growth and drought
Growth Form (according to Raunkiær Life-form classification)
Life History and Behavior
More info for the term: phenology
Smooth brome undergoes fall green-up. Inflorescences are initiated
during cool, short fall days . In colder climates, smooth brome is
dormant in winter. It may remain green year-round in southern climates
. Spring growth begins early in the season [110,107]. Lengthening
culms expose the panicles in late spring to early summer , and
smooth brome flowers in summer. In Minnesota, flowering occurred from
early to late June [80,86]. It occurred in late May or early June in
Ames, Iowa, with later, sporadic flowering . Phenology is delayed
in northern latitudes and high elevations. Smooth brome on the Wasatch
Plateau of Utah flowers 85 to 102 days after snowmelt . Seed
matures in early to late summer . Smooth brome grows throughout the
growing season when soil water is adequate. Under dry soil conditions
it becomes dormant, but it resumes growth when soils moisten .
Smooth brome is a cool season grass, beginning its growth early in the spring and growing late into the fall. New shoots emerge in the Chicago region as early as mid-March, when night temperatures are below freezing (Lamp 1952). Flowering primordia first become observable in early April in the Chicago region (Lamp 1952, Gall 1947) reaching 1 to 1.5 cm in length by early May near Ames, Iowa (Knobloch 1944).
Stem elongation varies from early May (Reynolds and Smith 1962) to late April in Wisconsin and Illinois (Lamp 1952). Boot stage is reached in mid-to-late May in Illinois and Wisconsin (Lamp 1952, Reynolds and Smith 1962, Knieval et al. 1971, Okajima and Smith 1964). In Illinois, plants are fully headed and blooming occurs during the first two weeks of June (Lamp 1952) whereas in Alberta, full head occurs in mid-June and pollination in July (Evans and Wilsie 1946). Seeds ripen in July in Illinois (Lamp 1952) and in August in Alberta (Evans and Wilsie 1946). Carbohydrate levels are lowest in the spring when the plant is at boot stage, but increase during internode elongation until heading (Teel 1956). In Wisconsin field studies, Reynolds and Smith (1962) report maximum total stored carbohydrates in mid-July when seed is mature, with smaller peaks in earliest spring in the pre-boot stage and in the fall.
Because of the importance of smooth brome as a forage crop, reliable seed crops are necessary and numerous studies have been conducted to determine the requirement for floral initiation and optimal conditions for seed production.
Smooth brome generally requires a period of vernalization under short day conditions followed by a long photoperiod for panicle production (Newell 1950, Kirshin et al. 1974, 1977) best fulfilled by short autumn days and longer spring days. The required time of exposure to low temperatures is short, 1 to 14 nights (Gardner and Loomis 1951) enabling some early- emerged spring shoots to grow under short days of early spring, be vernalized during a cold spell, and develop flowering panicles within the same year.
In greenhouse studies in the Chicago area, Lamp (1952) found a relationship between internode elongation and reproductivity. A minimum of 5 to 14 leaves must be developed during or before primordia formation if the plant is to flower in any given year. Flowering occurs at daylengths of 17 to 18 hours (Gall 1947, Evans and Wilsie 1946) when temperatures are warm. In Alberta studies Evans and Wilsie (1946) observed little flowering when air temperatures were below 60 degrees Fahrenheit.
Under experimental conditions the requirements for floral induction and flowering can differ from those reported above. Sprague (1948) observed some flowering in plants that had been maintained in a heated greenhouse and Allard and Evans (1941) report a critical period of 13 hours of daylength for flowering to occur.
Smooth brome is an open-pollinated self-incompatible species. Synchronous flowering is common (McKone 1985) with pollination occurring from plants up to 50 m away (Jones and Newell 1946). In Minnesota field studies seed set of open pollinated plants were 29% and in nurseries as high as 36% (Lowe and Murphy 1955) to 37% (Nielson 1951). The number of seeds produced has a very wide range. Lowe and Murphy (1955) report 47 to 160 seed heads per plant, with 156 to 10,080 viable seeds per plant. Maturing seeds are subject to predation by Itonidid midges and Chalcid flies (Nielson and Burks 1958). Kramer (1975) suggests that seeds may be transported and sequestered by ants, resulting in creation of new brome patches on anthills.
Smooth brome is a rhizomatous, sod-forming species. The first adventitious roots develop within 5 days of germination (Knobloch 1944). Rhizome formation begins as early as 3 weeks after germination (Wagner 1952) to as late as 6 months (Knobloch 1944).
The drought resistance of smooth brome is probably accounted for in part by its deeply penetrating root system. Dibbern (1947) reports Bromus roots reaching a depth of 4.7 feet. Lamba et al. (1949) found 21% by weight of brome roots between depths of 16 and 40 inches, 10% between 8 and 16 inches and 64% in the top 8 inches. This heavy concentration of total root mass near the surface is the result of smooth brome's creeping rhizomatous habit. Individual rhizomes are reported to have a longevity of one year (Evans and Ely 1935). Old brome fields develop a "sod bound" condition in which shoot density is reduced and symptoms of nitrogen deficiency are exhibited (Meyers and Anderson 1942). Benedict (1941) attributes this condition to a carbon/nitrogen imbalance (perhaps because of the sheer mass of dead rhizomes) but Grant and Sallans (1964) suggest that the decomposing roots may actually produce an allelopathic substance inhibitory to further brome root development.
Molecular Biology and Genetics
Barcode data: Bromopsis inermis
Statistics of barcoding coverage: Bromopsis inermis
Public Records: 2
Specimens with Barcodes: 9
Species With Barcodes: 1
Barcode data: Bromus inermis
Statistics of barcoding coverage: Bromus inermis
Public Records: 22
Specimens with Barcodes: 32
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: NNA - Not Applicable
Rounded National Status Rank: N4 - Apparently Secure
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status (e.g. threatened or endangered species, state noxious status, and wetland indicator values). This plant has threatened status in Michigan.
Global Short Term Trend: Increase of 10 to >25%
Comments: Smooth brome has been widely planted as a forage and cover crop. Although perhaps not as invasive as Poa pratensis, with which it often grows, it is highly persistent. It forms a dense sod that often appears to exclude other species, thus contributing to the reduction of species diversity in natural areas. Within the Rocky Mountain range of the native Bromus pumpellianus, hybrid introgression is occurring and disjunctive hybrid plants have also been found in the Great Lakes Region (Elliot 1949).
Pests and potential problems
Grasshoppers and seedling blight are influences that may impede establishment. Foliar diseases are more common in humid areas and seasons. The bromegrass seed midge, Stenodiplosis bromicola, can seriously hinder seed production.
Management Requirements: Bromus inermis has become established in overgrazed pastures and old fields, especially around the edges and in haystack areas. It is most often a problem in discrete patches which would appear to be amenable to selective treatment, but also appears to be invading native prairie from roadsides.
One of the difficulties in understanding how best to manage for Bromus inermis is that because of its cool season habit it is often lumped together with Poa pratensis both in research results and management decisions. Yet it appears from the species' biology and its response to various management experiments that there is a difference in the timing of the most susceptible phenological stages of the two species. Because there is some overlap in the species' times of vulnerability to fire or defoliation, dual management produces partial control of Bromus. Casual observation of the two species in southwestern Minnesota suggests that there can be a 2 to 2 1/2 week lag period between the optimal spring fire date for Poa (before it is in flower) and that for Bromus (when it is still in boot) (Sather, personal observation).
More effective management of smooth brome might be achieved by first understanding the relative proportions of Bromus inermis and Poa pratensis and their spatial distribution in the mosaic of the vegetation. Treatment schedules could then be adjusted to impact smooth brome in the boot stage in areas where it is the rightful target species.
MECHANICAL: Both experimental studies and management experience indicate that cutting smooth brome in the boot stage, i.e. while the flowering head is still enclosed within the sheath, is perhaps the most effective means of control. Martin (pers. comm.) reports successful reduction of Bromus inermis in Minnesota test plots when cut during boot stage, which occurs the time it reaches a height of 18 to 24 inches, in late May. The best conditions for damage are hot, moist weather at the time of cutting, followed by a dry period (Martin pers. comm). Experimental studies comparing the effects of growth stage and height at time of cut in Saskatchewan suggest that the greatest subsequent winter injury can be attained by cuttings at the shot blade stage (i.e just before the plant changes from vegetative to early elongation of reproductive stage) than by waiting until flowers have developed (Lawrence and Ashford 1964). Cutting at 3.8 cm produced greater subsequent winter injury than did cutting at progressively taller heights up to 14 cm (Lawrence and Ashford 1964). Cutting at "shot blade" or "boot" stage just after the apical meristem has begun to elongate within the sheath takes advantage of the low root carbohydrate levels at that time (Paulsen and Smith 1969, Reynolds and Smith 1962, Knievel et al. 1971).
Carbohydrate levels can be kept at slightly lower than normal levels throughout the summer by repeated cuttings (Paulsen and Smith 1968). Martin and Hovin (1980) found in Minnesota field trials that persistence of smooth brome over a 4-year period was more greatly reduced by 4 cuts a year than by 2 or 3 cuts. However, it should be noted that their experimental results are somewhat confounded by the fact that only the 4- cut schedule included a cut during the boot stage. Paulsen and Smith (1968) found that bromegrass harvested in boot was as adversely affected as plants managed under a 3-cut harvest schedule. Slow recovery was associated with the removal of apical meristems when tiller buds were poorly developed.
It therefore appears that a single well-timed close cut in boot stage (approximately 18 inches) may be an effective method of control. Managers of natural areas such as parks might wish to try repeated lawnmowing of brome beginning in late May and mowing at least 4 times during the season where brome patches are contiguous and pure.
FIRE: Fire does not appear as effective in reducing smooth brome as it is with Poa pratensis. Kruse (pers. comm.) reports that in North Daktoa smooth brome can be kept from spreading, but not appreciably reduced with fire. Old (1969) reports decreases in July dry matter production but not elimination of smooth brome after April fire in Illinois. One difficulty in assessing the effectiveness of burning for control of Bromus inermis is the dearth of literature that clearly separates this species from "cool season exotics" as a group.
Cosby (1972) reports the comparative effects of late May mowing and June 1 burning at Lake Andes National Wildlife Refuge, North Dakota. There biomass production in August of the treatment year was 80 lb/acre of Bromus inermis following mowing and 5 lb/acre following burning. These data suggest that a well-timed burn that treats Bromus in boot (or early bloom?) may be more effective than mowing at the same susceptible period. At Kilen Woods State Park, Minnesota, there was no visible, discernible reduction in Bromus in the first or second season after an April 22 burn (Sather 1986, 1987, pers. obs.). At Lostwood National Wildlife Refuge where nine years of burning have followed a summer schedule (mid-June and late July to mid-August) to reduce woody encroachment, smooth brome has actually increased in areas that formerly had heavy litter build-up or dense Symphoricarpos growth (Smith, pers. comm.). There, May burns are planned to help target the bromegrass. It appears that late May burns would be optimal in the northern plains for reduction of smooth brome.
HERBICIDES: Several chemicals have been tried to control cool season grasses for the purpose of sod-seeding legumes and improving pastures.
In an early study of brome control, McCarty and Scifres (1966) tested picloram, dicamba and 2,4-D and found picloram most effective at rates of 1.1 to 2.2 kg/ha, dicamba somewhat less effective and 2,4-D ineffective.
In pastures where increased legumes are desired, late April applications of paraquat, glyphosate and atrazine at 2.24 kg/ha and glyphosate at 1.12 kg/ha have been used successfuuly to shift dominance from cool to warm season grasses on Nebraska rangelands (Waller and Schmidt 1983). Herbage yields of smooth brome from atrazine treated plots were not significantly different than from glyphosate treated plots. An application of this technique is presently in the experimental stage in a brome-infested area of Sioux Prairie, South Dakota (Wells pers. comm.).
Dalapon and pronamide have been used to suppress or kill smooth brome during the establishment of birdsfoot trefoil (Martin et al. 1983, Rayburn et al. 1981). In Minnesota trials Martin et al. (1983) found both dalapon (at rates of 3.4 to 9.0 kg/ha) and glyphosate (at rates of 0.6 to 1.1 kg/ha) more effective in April and May than in June applications. In New York trials Rayburn et al. (1981) found glyphosate at 2 kg/ha more effective than dalapon (at 3.0, 4.0 and 9.0 kg/ha) or pronamide (at 0.4, 1.0 and 2.0 kg/ha). In the same study, rates of application of glyphosate as low as 0.5 kg/ha produced some effect but control was better as rates approached 2 kg/ha. In Nebraska field trials Vogel et al. (1983) found paraquat somewhat less effective than glyphosate in April applications to control smooth brome. It appears that April or May applications of glyphosate at 2 kg/ha may be an effective management technique for controlling smooth brome in pure patches.
Management Programs: Management programs in which Bromus inermis has been specifically singled- out as the target species are few. The following individuals are involved in programs that specifically target smooth brome:
Karen Smith, Refuge Manager, Lostwood National Wildlife Refuge, R. Rt. 2, Box 98, Kenmare, N.D. 58746.
Dr. Darrell Wells, Route 4, Box 233, Brookings, South Dakota 57006.
Dr. Gary Larson, Dept. of Biology, Ag. Hall 304, South Dakota State University, Brookings, S.D. 57007.
Monitoring Programs: Permanent markers have been placed at the edge of brome patches at the Helen Allison Savannah, Minnesota, to allow for tracking of these patches over time. contact: Dr. D.B. Lawrence, 1420 34th Ave. South, Minneapolis, MN 55406. 612/729-8206.
The following individuals are monitoring the frequency and/or cover of Bromus as a measure of responses to prairie management practices:
Arnold Kruse, Northern Prairie Wildlife Research Center, P.O. Box 1747, Jamestown, N. Dakota 54801.
Karen Smith, Refuge Manager, Lostwood National Wildlife Refuge, R.Route 2, Box 98, Kenmare, ND 58746.
Bromus patches at Sioux Prairie, South Dakota, are being monitored to measure success of eradication methods using herbicides. Contact: Dr. Gary Larson, Dept. of Biology, Ag. Hall 304, South Dakota State University, Brookings, SD 57007.
Bromus is one of several species being monitored as part of a dissertation study on old field succession at the Cedar Creek Natural history Area, Minnesota. Contact: Barb Delaney, Dept. of Botany, University of Minnesota, St. Paul, MN.
Management Research Programs: The only research program specifically addressing control of smooth brome is that at Sioux Prairie, South Dakota, where response of bromus to atrazine is being tested. Contact: Dr. Gary Larson, Dept. of Biology, Ag. Hall 304, South Dakota State University, Brookings, South Dakota 57007.
Management Research Needs: Bromus is often considered in conjunction with Poa pratensis in management programs because both are rhizomatous, cool season exotic grasses. There is a need to relate the dates of management procedures specifically to the physiological/phenological growth stage of Bromus at the time of management and to directly measure the response of Bromus separate from Poa.
Some specific research questions that would appear to be useful to managers of natural areas in their attempts to understand and control Bromus include: Is a single cut in boot as effective in reducing Bromus persistence as the documented first cut in boot? (Most studies in which Bromus has been cut in boot have been addressing the frequency of cutting and the boot cut has been an artifact of efforts to increase cutting frequency.) Is burning in boot as effective as cutting in boot for lowering the persistence of Bromus over a period of years? What is the response of Bromus to fall fires and/or grazing, which might enhance survival of its native cool season competitors, particularly in the northern part of its range? What is the actual rate of invasiveness of Bromus into established prairie sod? Are chemical treatments such as atrazine as effective in pure brome stands as they are in mixed stands of brome and warm season natives?
Range: Smooth brome's tolerance to grazing is generally rated as high
. It is highly adaptable, having persisted in many of the habitats
where it was planted to increase forage production including
pinyon-juniper (Pinus-Juniperus spp.) , quaking aspen (Populus
tremuloides) , and subalpine and alpine ranges [56,102]. It has
persisted on old saltgrass (Distichlis spicata) meadows with saline
soils once the saltgrass was removed [84,85].
Smooth brome may not tolerate grazing on all habitat or site types.
Currie and Smith  reported that smooth brome planted on
low-fertility ponderosa pine (Pinus ponderosa) forest soils in Colorado
declined under even light-intensity cattle grazing. They speculated
that smooth brome is more likely to persist under cattle grazing on
Laycock and Conrad  used cattle to test several grazing systems on
rangeland seeded to crested wheatgrasses (Agropyron cristatum and A.
desertorum) and smooth brome in mountain big sagebrush (Artemisia
tridentata spp. vaseyana) habitat in Utah. They found that average
cattle weight gain was the same under all systems, but heavy June
grazing in alternate years best promoted grass production.
Ungulates in Yellowstone National Park utilized smooth brome growing in
association with other graminoids and forbs, but did not graze smooth
brome where it grew in a monoculture .
Forestry: In British Columbia, height and biomass of lodgepole pine
(Pinus contorta var. latifolia) seedlings established from a mix of
lodgepole pine seed and smooth brome and other grass seed were less
than height and biomass of lodgepole pine seedlings established from
lodgepole pine seed sown alone .
Native grassland restoration: Smooth brome dominates many native
grasslands and old fields . Masters and Vogel  stated that on
tallgrass prairie, it is usually found in areas with a history of
overgrazing and/or fire exclusion. Grassland restoration efforts often
include controlling smooth brome with cool-season grass herbicides such
as atrazine and glyphosate, mowing, and/or prescribed fire .
Anderson  found that near Lincoln, Nebraska, fall application of
glyphosate helped control smooth brome. Atrazine may not be as
effective; other studies [83,96] have reported that while atrazine
controlled other exotic cool-season grasses, it did not significantly
reduce smooth brome.
Establishment and maintenance: Seed handling and planting guidelines
for smooth brome are available [49,116,117]. Cultivars adapted to
selected environments and/or regions are sold commercially
Smooth brome requires fertile soil in order to maintain nutritional
quality. On infertile soils it needs periodic fertilization or a
companion nitrogen fixer. On rangelands smooth brome is usually planted
in a mix with alfalfa (Medicago sativa), yellow sweet clover (Melilotus
officinalis), or other legume species. Fertilization affects growth
allocation: Watkins  found that fertilizers increased leaf and
shoot growth but reduced rhizome and root growth.
Rhizomatous cultivars become sod-bound after several years unless litter
is removed by grazing and/or fire [56,110].
Cultivars, improved and selected materials (and area of origin)
Northern type cultivars: ‘Superior’, ‘Manchar’, ‘Carlton’, ‘Jubilee’, ‘Saratoga’ (various), ‘Polar’, ‘Bravo’
Southern type cultivars: ‘Lincoln’ (Hungary), ‘Achenbach’, ‘Elsberry’, ‘Lancaster’, ‘Lyon’, ‘Southland’, ‘Rebound’, ‘Baylor’ (various), ‘Beacon’
Smooth brome requires heavy early spring and fall applications of nitrogen to maintain high yields in a pure stand. Mixtures with alfalfa will require less nitrogen but the alfalfa will usually need P205 each year to maintain vigor. Alfalfa cannot be maintained in pasture seedings without rotation. Best forage production is obtained from smooth brome when used in a planned cropping system and plowed out after 3 to 4 years. Its heavy sod makes it an excellent soil conditioning crop when included in cropping systems. In deep, well-drained soils it will root to 4 feet.
Smooth brome performs best in grassed waterways, field borders, and other conservation uses where the forage can be cut and removed while in early bloom. Do not graze the new seeding; cut the first crop for hay.
In bromegrass-legume pastures, allow the legume to go to bud or early-bloom stage before turning cattle in to avoid bloat hazard, and manage thereafter for
optimum regrowth of the legume. Pastures should not be grazed prior to smooth brome attaining a minimum height of about 10 inches at the beginning of the grazing season. Grazing pressures should be adjusted throughout the season to avoid grazing this grass to less than a minimum height of 4 inches. Grazing schedules should be so arranged that a regrowth period of 28 to 35 days between grazing periods is available.
This plant may become weedy or invasive in some regions or habitats and may displace desirable vegetation if not properly managed. Please consult with your local NRCS Field Office, Cooperative Extension Service office, or state natural resource or agriculture department regarding its status and use. Weed information is also available from the PLANTS Web site at plants.usda.gov.
Relevance to Humans and Ecosystems
Uses: FORAGE/BROWSE, Pasture
The cover value of smooth brome has been rated as follows :
UT CO WY MT ND
upland game birds fair ---- ---- good good
waterfowl fair ---- ---- ---- fair
small nongame birds good fair ---- fair fair
small mammals good fair ---- good ----
The National Academy of Sciences  found the nutritional content of
fresh, flowering smooth brome in the United States was as follows:
dry matter (%) 27.1
ash (%) 1.9
crude fiber (%) 8.3
ether extract (%) 0.9
N-free extract(%) 13.2
protein (%, N x 6.25) 2.8
digestible energy (Mcal/kg)
domestic sheep 0.78
Nutritional content of fresh smooth brome in immature, early bloom,
milk, dough, overripe, and weathered stages, and of cured smooth brome
in each stage, is also available .
The nutritional value of smooth brome for wildlife has been rated as
UT CO WY MT ND
elk good good ---- poor ----
mule deer good fair ---- ---- poor
white-tailed deer ---- ---- ---- ---- poor
upland game birds good ---- ---- ---- poor
small nongame birds fair ---- ---- ---- ----
waterfowl fair ---- ---- fair ----
small mammals good good ---- ---- ----
nutritional quality drop rapidly after flowering. Fall green-up
provides palatable forage later in the year .
The palatability of smooth brome has been rated as follows :
UT CO WY MT ND
cattle good good good good good
domestic sheep good good good good good
horses good good good good good
Importance to Livestock and Wildlife
Livestock: Smooth brome cultivars have been bred for nutritional
quality and adaptation to selected climates. This has made smooth brome
one of the most important exotic forage grasses in the United States and
Canada. It is widely planted in pastures and rangelands from Texas to
Alaska and Yukon Territory [87,88,110].
Wildlife: Grazing wildlife utilize smooth brome to varying degrees,
depending upon wildlife species and smooth brome quality. Elk use it as
a winter food . Mule deer in central Utah were found to use it only
lightly , but deer utilization of smooth brome is generally
considered good [40,110]. Geese  and small rodents such as pocket
gophers  also graze smooth brome. The seeds may not be preferred by
granivores. Everett and others  found that when offered the seed of
18 herbaceous species, deer mouse selected smooth brome seed the least.
Smooth brome provides cover for birds and small mammals . Ducks,
[33,78], gray partridge , American bittern, northern harrier, and
short-eared owl  use it as nesting cover.
Value for rehabilitation of disturbed sites
hardy and fairly resistant to saline soils and drought . The
ability of most cultivars to spread rhizomatously makes smooth brome a
good soil binder [56,103,104]. It is recommended for erosion control
and streambank and stream bottom stabilization in all areas of the
United States except the Southeast [104,118]. Southern cultivars tend
to be more strongly rhizomatous than northern cultivars, and generally
give the best erosion control . Some southern cultivars will grow
in northern latitudes of the United States . Smooth brome has also
been successful in rehabilitating mined lands [38,43], game ranges
[51,65], roadsides , and ski areas . Smooth brome establishes
on high-elevation sites . It can be an aggressive colonizer on many
sites, however, and may crowd out native species .
Smooth brome showed poor survivorship on semiarid canyonland in
northwestern Idaho that was disked and seeded with several grass species
to remove yellow starthistle (Centaurea solstitialis) .
Livestock: Smooth brome may be used for hay, pasture, or silage. It is compatible with alfalfa or other adapted legumes. The grass is highly palatable and is high in protein content and relatively low in crude-fiber content.
Erosion Control: Since the plant has a massive root system and is a sod former it can be used effectively for critical area planting and grassed waterways if the areas can be irrigated or where annual precipitation exceeds 20 inches.
Wildlife: Smooth brome can be used as a component in various upland wildlife and conservation cover mixes for nesting cover and food. Note: This species is no longer recommended for wildlife use in some states because of its aggressive nature.
Stewardship Overview: Smooth brome is a cool season exotic that is especially troublesome in disturbed portions of old pastures in the tallgrass and mixed prairie regions. Although less invasive than Kentucky bluegrass, with which it often occurs and is managed, it is also less responsive to management.
The optimal timing for control of smooth brome by burning appears to be in boot stage, which may be as early as mid-April in the central Great Plains or in the northern plains. This is somewhat later than would be recommended for other management purposes such as control of Kentucky bluegrass. However, its habit of occurring frequently in nearly pure swards renders Bromus inermis a good target for selective control by timed close mowing or use of herbicides. One close mowing when the plants are 18-24 inches tall (followed ideally by 3 repetitions), or treatment with glyphosate at 0.5 to 1.1 kg/ha before flowering, may improve chances of selectively controlling this species.
The plant is characterized by an erect, leafy, long-lived perennial, 46 to 91 cm (1 1⁄2 to 3 ft) tall, rhizomatous and commonly producing a dense sod. It starts growth in early spring; flowers May to July; reproduces from seeds, tillers, and rhizomes. It may regrow and re flower in the fall if moisture is sufficient. The leafs are glabrous or occasionally pubescent, particularly on the sheaths; blades 20 to 38 cm (8 to 15 in) long, 0.6 to 1.3 cm (1⁄4 to 1⁄2 in) wide, flat, with a raised and keeled midrib below; sheaths closed, except near collar, and papery when dry; leaves rolled in the bud; ligates up to 0.3 cm (1⁄8 in) long, rounded, and membranous; auricles absent.
- Arctic brome – English [Bromus inermis subsp. pumpellianus]
- Austrian bromegrass – English [Bromus inermis subsp. inermis]
- awnless brome – English [Bromus inermis subsp. inermis]
- Hungarian brome – English [Bromus inermis subsp. inermis]
- Hungarian bromegrass – English [Bromus inermis subsp. inermis]
- Pumpelly's brome – English [Bromus inermis subsp. pumpellianus]
- Russian bromegrass – English [Bromus inermis subsp. inermis]
- smooth brome – English [Bromus inermis subsp. inermis]
- smooth bromegrass – English [Bromus inermis subsp. inermis]
- brome inerme – French [Bromus inermis subsp. inermis]
- brome sans arêtes – French [Bromus inermis subsp. inermis]
- unbegrannte Trespe – German [Bromus inermis subsp. inermis]
- wehrlose Trespe – German [Bromus inermis subsp. inermis]
- capim-cevadilha – Portuguese [Bromus inermis subsp. inermis]
- bromo de Hungría – Spanish [Bromus inermis subsp. inermis]* bromo inerme – Spanish [Bromus inermis subsp. inermis]
A very useful fodder grass introduced into the British Ises and North America for this reason.
Names and Taxonomy
Comments: Treated in most older floras as native to Europe, however, if the w. U.S./Canada native B. pumpellianus is included as a subspecies of B. inermis (as in Kartesz 1994), the full species is considered native to these countries as well. Kartesz 1999 includes 'pumpellianus' in Bromus inermis as a subspecies, as well as two varieties of B. inermis ssp. pumpellianus (B. inermis ssp. pumpellianus var. arcticus and B. inermis ssp. pumpellianus var. pumpellianus). Subspecies pumpellianus and its varieties are considered native to North America while the other subspecies of Bromus inermis, B. inermis ssp. inermis is non-native.
The currently accepted scientific name of smooth brome is Bromus inermis
Leyss. Infrataxa are [54,61,68]:
B. inermis ssp. inermis Leyss
B. inermis ssp. inermis var. divaricatus Rohlena
B. inermis ssp. inermis var. inermis Leyss
Kartesz  recognizes Pumpelly brome as a subspecies of B. inermis, B.
inermis ssp. pumpellianus (Scribn.) Wagnon. FEIS follows the treatment
of other authorities in recognizing Pumpelly brome as a separate
species, B. pumpellianus Scribn. [54,58,61,67,115,121]. (A literature
summary of B. pumpellianus is available in FEIS.) Considerable
hybridization and introgression have occurred between smooth brome, an
introduced species, and Pumpelly brome, a native species [5,53,121].
Smooth brome does not hybridize with other North American species .
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