Despite the obvious, these pretty purple-flowered shrubs are indeed a yellow bush lupine. This was news to me! I didn’t even realize the two color types were the same species until I went to look up the Latin name. After all, I was sure I already knew the common name: purple bush lupine, right?
Wrong. No such plant exists, according to the field guide. So I turned to the key—and couldn’t find it! The darn thing kept keying out to yellow bush lupine (Lupinus arboreous). There are other purple, shrubby lupines (silver lupine and dune bush lupine) but both have distinctively hairy upper petals. This one didn’t. I’m embarrassed to admit that it took a long time for me to read through to the second page of the yellow bush lupine species description where I found the explanation: “It is usually yellow, but always yellow-flowered in the dunes and blue-flowered in the coastal scrub, bishop pine forest, and elsewhere.” The species is also sometimes called coastal bush lupine, which I think is a much better name!
Whatever their name and whatever their color, these lush shrubs dish out fragrant towers of blossoms. They can grow to be as tall as a person, though often are knee height or lower: spreading mounds of silky-haired, fan-shaped leaves. Look for them on sand dunes and hillsides from Washington state to San Diego. They cling to cliffs and roadsides and are very popular among insects—and rodents too! Each plant produces hundreds of seed pods that our furry friends love to munch.
Flowers Of Marin 