Biology/Natural History: A. xanthogrammica is basically a solitary species and can occur in numbers up to 14 per square meter if conditions are favorable. They are vividly green if they are exposed to bright sunlight. The bright green can be attributed to green pigment in the anemone epidermis and to symbiotic algae that live in the tissues that line the gut. Inside there may be zoochorellae (green algae) or zooxanthellae, which are dinoflagellates. The symbiotic algae are reduced in numbers or even absent (aposymbiotic) when in shady areas. The anemones release sperm and eggs in late spring to summer. The larvae swim or float freely, dispersing. The adults do not split in half asexually, as is so characteristic of its congener A. elegantissima. They eat detached mussels, sea urchins, small fish, and crabs. I have also commonly seen them spitting out empty barnacle plates so I suspect they will eat barnacles as well. Mussels seem to be a primary item in the diet. Predators include the seastar Dermasterias imbricata. The sea spider Pycnogonum stearnsi is often found around the base in central California and the large amoeba Trichamoeba schaefferi may be found as well. In southern California the snail Opalia borealis, which feeds by inserting its proboscis into the column, may be on the base and the wentletrap snail Epitonium tinctum may also be found. Epitonium tinctum feeds on the anemone's tentacles at high tide.
Cnidae in this species include Spirocysts, atrichs, basitrichs, and microbasic p-mastigophores.
This is one of the largest species of anemone in the world. Some Antarctic species and tropical anemones on coral reefs grow larger. It does not survive well in areas with sewage or other pollution.