Flower:

Flowers are in flat clusters (umbels) 1½ to 2 inches across, in groups (umbellets) of 10 to 20 flowers each. Clusters are at the top of the plant and at the end of stems that arise opposite the leaves. Individual flowers are white, about 1/8 inch across with 5 notched petals of unequal size, a creamy white center and 5 white to pink stamens. The flowers on the outer edge of an umbellet open first; the unopened flowers may have a pinkish tinge.

At the base of an umbel are 2 or more vary narrow bracts that may be slightly spreading. Up to 8 bracts are at the base of each umbellet, though they are very small and hard to see.

Leaves and stem:

Leaves are compound in groups of 3 to 5, up to 5 inches long, 4 inches wide, alternately attached with a small sheath where the leaf stalk joins the stem. In the lower part of the plant, leaflets are feathery and fern-like. Leaves near the flowers at the top of the plant are smaller and less deeply divided.

Leaves and stems are covered in stiff, appressed hairs giving them a rough texture. Stems are erect, ridged and branched.

Fruit:

Fruit is oval, about 1/8 inch long and covered in hooked hairs. It ripens to brown and splits into 2 seeds. The hooks attach the seed to nearly anything that comes in contact with it and help it spread.

Notes:

This is a relatively recent introduction to Minnesota, first reported in 2009 from Battle Creek Park in St. Paul, where it was found to be widespread. It has since spread across the metro area and beyond, found as far away as Renville and Lake counties. The most current distribution info can be found on EDDMapS. In the majority of cases, it's established along hiking and bike trails, campgrounds and other recreational areas, which means people are tracking it in on footwear, tires and dogs. We cannot emphasize strongly enough the importance of cleaning your gear!

Wisconsin saw its potential to form large populations and designated it a prohibited/restricted species years ago. Minnesota's Weed Advisory Group completed a risk assessment on this species in 2015 and determined that, since at that time (in MN) it wasn't forming monocultures in high-quality habitat and did not appear to reach densities of more than 50% where it did establish itself, it did not warrant any special status. So it's left to run wild except for the efforts of dedicated land managers and volunteers, and there aren't nearly enough of them.

There are several species of carrot with small white flowers and feathery leaves and it's not hard to confuse them all. Emerging leaves in May might be mistaken for Queen Anne's Lace (Daucus carota) but once it starts flowering it is obviously something else, since Queen Anne's Lace has large, showy bracts. A good way to ID this is by the few, narrow bracts at the base of the umbel—that along with the stiff, appressed hairs on leaves and stems, and the hooked hairs on the fruits are a unique combination. Early in the season the plants look open and airy but fill in with many branches as they mature. It seems to have a preference for moist soil and part shade, but apparently will grow almost anywhere. If you see it, kill it.