Flower:

One to 3 stalked flowers arising from leaf axils and at the tips of branching stems. Flowers are ¼ to 1/3 inch across with numerous white ray flowers (petals) around a broad center disk of tiny white to creamy white disk flowers.

Cupping a flower is a set of 8 to 10 green bracts, lance-shaped with pointed tips and usually of unequal size. Bracts and flower stalks are sparsely to densely covered in appressed hairs.

Leaves and stems:

Leaves are opposite, 1 to 4 inches long, up to 1 inch wide, shallowly or minutely toothed around the edges, lance-elliptic to lance-linear, pointed at the tip, and stalkless at the base or nearly so. Both surfaces are sparsely to moderately covered in appressed hairs. Stems are single from the base, branched, covered in appressed hairs, often purple, and weak—erect to ascending when supported by surrounding vegetation, otherwise more sprawling and the branches rooting at the lower nodes.

Fruit:

The center disk becomes a seed head, expanding to about ½ inch diameter at maturity. Fruit is a dry seed less than 1/8 inch long, somewhat cone-shaped in outline, flattish across the top, 4-sided, lacking a tuft of hairs, and drying to dark brown. Both disk and ray flowers are fertile.

Notes:

Yerba-de-tago has only been recorded twice in Minnesota, the first in 1976 along the St. Croix River just south of Afton, and the second just a few years ago in the backwaters of the Mississippi River at Spring Lake Park. The MN DNR does not consider it native in the state, but we think that is questionable, especially considering it is a Special Concern species in Wisconsin. Minnesota would be at the northern tip of its range. In the greater part of its range it's a somewhat weedy species, usually found in the disturbed soils of river bottoms, shores, wet ditches, grassy hollows and other muddy places, though occasionally found in drier locations. At Spring Lake Park, it's found on a few sand bars a short canoe ride from the river bank. It may have been deposited there recently by bird or boat, or has possibly been there but undetected for many years—we will never know for certain.

It is not likely to be mistaken for any other species, distinguished by: the relatively short stature, numerous often sprawling branches, opposite lance-linear to lance-elliptic leaves, appressed hairs over most of the plant, 1 to 3 small fleabane type flowers in leaf axils, and seed that lacks a tuft of hairs. Yerba-de-tago has a long history of medicinal uses, including an antidote for snakebite venom, treatment for liver disorders, and even to prevent balding. Pretty versatile stuff, eh?