In my previous post (“Desert Madwort”) I noted that desert madwort (Alyssum desertorum), introduced from Eurasia and now naturalized throughout Western and Central North America, closely resembles anotherEurasian invader, yellow alyssum (Alyssim alyssoides). These two plants are so similar that they are difficult to tell apart. I rely on the seed pods to distinguish the two species. Desert madwort has glabrous (no hairs) pods while the seed pods of yellow alyssum are hairy. Otherwise, to my amateur eye, the two plants appear the same.
Yellow alyssum is the more common of the two “look-alike” alyssums and can be found in dry gravelly ground, croplands, wastelands and other disturbed areas throughout all of North America except North Dakota, New Hampshire and a few Southern States. As with its lookalike, desert madwort, yellow alyssum can invade croplands and pastures and be considered a noxious weed.
Yellow alyssum is also commonly called pale madwort, Alison, and yellow Alison, among other names. Apparently Allison was how the genus name sounded to someone.
I only included pictures of a mature yellow alyssum plant and pictures of the seed pods in this post since the pods are a primary identifying characteristic. The desert madwort plant photos in my previous post are indistinguishable from yellow alyssum – only the hairy seed pods are different.
This yellow alyssum plant was growing along the roadside south of Bieber CA (Lassen County).