Field Guide

Called carpenter’s weed for its remarkably square stems, cup plant is also notable for its large, opposite leaves that fuse around the stem to form a leafy cup that holds rainwater.

“Infestation” is the term for what teasels are doing in Missouri. Learn to identify these thistlelike plants, and help to control the weedy spread of these tough, prickly invaders.

Large stands of wind-pollinated giant ragweed commonly form in disturbed areas, causing late-summer misery in the form of hay fever for many Missourians.

Tickseed sunflower has flattened black seeds that attach themselves to clothing and pets via two needlelike awns. In flower, it grows in massive displays in moist bottomlands.

Narrow-leaved vervain is a short, slender perennial with single stems or with upper stems sparingly branched. Its many small flowers are crowded on narrow spikes. The corollas are tubular, deep lavender or purple, with 5 spreading lobes.

Sometimes called wild oregano, dittany, like true oregano, is a member of the mint family and can be used as a culinary herb and in teas. Look for it on dry, wooded slopes in Ozark counties.

You can find small colonies of lance-leaved loosestrife nearly throughout the state. It has showy but nodding yellow flowers and opposite, closely spaced, lanceolate or ovate leaves.

Leaf cup is named for the leafy appendages that wrap around the stem at the bases of the opposite leaves. Part of the sunflower family, leaf cup has about 8 white ray florets surrounding yellow disk florets.

The scarlet pimpernel, a native of Europe, is a tender annual with scarlet or brick-red flowers that close around 4 p.m., or whenever clouds shade the sun. When the sun comes out again, they reopen.

Square, unbranching stems, opposite leaves, two-lipped flowers, and a mild minty fragrance are clues Ohio horsemint is in the mint family. Tight, rounded flower clusters are stacked atop one another at the stem tips.