Field Guide

In Europe, St. John’s-wort was long used as a medicinal herb and to ward off evil magic. Today, researchers are finding it can treat depression. Yet it poisons livestock and in some places is an invasive weed.

Water milfoils are feathery aquatic plants that grow rooted in shallow water. Their tips emerge above the waterline and bear bladelike, toothed leaves.

Naiads are slender, narrow-leaved plants that grow completely under water and are rooted to the bottom. They never have broad, floating leaves or conspicuous flowers or seed heads.

“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.

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.

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.

Even without its flowers, or its fruits that resemble miniature oranges, common horse gentian is notable for its opposite leaves, which are broadly fused together at the bases and almost appear as a single leaf with a stem going through it.

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.

A square-stemmed plant with opposite leaves, self-heal bears two-lipped blue, lavender, or violet flowers in a cylindrical head. We have two varieties of self-heal in Missouri, one native and one introduced.