Flower:

Loose, flat clusters of bright yellow, dandelion-like flowers, each up to 2 inches wide, at the ends of slender, branched stalks. While individual stalks may produce numerous flowers over the growing season, rarely are more than a few blooming at any given moment; some are producing seedheads while other buds are just developing. New flowering stalks will also emerge from lower stem leaf axils as the plant matures and older stalks stop flowering and wither away or are broken or mowed off. This variety of perennial sowthistle, var. glabrescens , is smooth all over, while its other varietal form, var. arvensis , has bracts and flower stalks that are densely covered in fine bristly hairs.

Leaves and stem:

Leaves have soft, spiny toothed edges that may be wavy, are hairless, mostly with small rounded lobes at the base that clasp the stem. Lower leaves are up to 2 inches wide and to 12 inches long and are somewhat variable in shape, having shallow or deep rounded lobes, occasionally unlobed. They tend to be crowded on the stem.

Leaves rapidly shrink in size as they ascend the stem. Upper leaves are generally unlobed and widely spaced on the stem, though most leaves are confined to the lower half of the plant. The flower stalk emerges from basal rosettes. Var. arvensis is densly, fine bristled throughout the stem.

Fruit:

Fruit is dandelion-like plume of dark brown seeds with pure white hairs to carry them off in the wind.

Notes:

This species is a rapid colonizer from deep, extentive underground root systems. Listed as a Minnesota state primary noxious weed, it is now widely established throughout its preferred MN range but is not as problematic agronomically as was once feared. Still it would have been best if it had never arrived here in the first place. This species may be de-listed as a state primary noxious weed. Var. glabrescens is common throughout much of Minnesota, var. arvensis has only been reported in a few counties, mostly in western MN. It is similar in appearance to Sonchus asper (Spiny Sowthisle) and Sonchus oleraceus (Common Sowthisle). Spiny Sowthistle has decidedly larger spiny teeth on the leaves and larger lobes at the leaf base, and flowers typically less than 1 inch across. Common Sowthistle has more angled lobes on the leaves and flowers that are also 1 inch or less.