What are those little yellow weeds?

Have you noticed the carpets of a little mustard-like yellow flower this year? The patches seem to be everywhere from road ditches to hay fields to pastures.

You are likely seeing either desert or yellow alyssum, members of the Mustard family. Both species grow at low to mid-elevations in disturbed soils of grasslands, steppe, streambanks, or roadsides, as well as rocky areas. Yellow alyssum can invade undisturbed areas and grow with established perennial bunchgrasses. Desert alyssum is potentially a weaker invader that requires the site to be disturbed before establishment. As annual plants,...