An attractive green lawn becomes a field of purple flowers. Three weeds in particular could be at the root of your lawn problem: henbit, purple deadnettle or wild violets. Henbit and purple deadnettle are broadleaved, winter annual weeds and are part of the mint family. Wild violets are a cool-season perennial, most visible in the spring and fall. They commonly grow in shady areas of the lawn and spread outward from there throughout the eastern half of the United States, according to the National Gardening Bureau. Knowing how to identify these weeds is the first step toward reclaiming an unmarred green lawn once again.
Look for subtle differences between the leaves on the plants to tell them apart. The leaves of henbit have a broad egg shape and blunt-toothed edges when they first emerge, as well as visible veins on the underside. The lower leaves grow on petioles, or stems, while the upper leaves are crinkly and attach directly to the main plant stem. Purple deadnettle leaves are hairless and triangular to heart-shaped, with round-toothed edges. The leaves and petiole length get shorter toward the top. The lower leaves are deep green, while the upper leaves overlap and are purple-red. Wild violets have medium green, kidney-shaped to oval leaves with heart-shaped bases on long petioles.
The stems of henbit and purple deadnettle are square, but henbit's stems have a green or purple colour with a scattering of hairs, while purple deadnettle has red stems. They grow to roughly the same height, with henbit reaching up to 16 inches tall and purple deadnettle up to 18 inches. Both have branched stems that spread outward. The stems of henbit have low-lying leaves at their base and the tips turn upward, unlike purple deadnettle, which does not. Violet is a low-growing, spreading plant that's close to the ground with no visible stems.
Violet's medium-purple flowers may have a white or yellow centre. They bloom on slender stalks that are lost in the foliage from April to June; the flowers seem to peek out from a spreading sea of green. The small purple clusters of tubelike flowers of henbit stick out from the tiny amount of foliage. Look closely to see the tiny purple flowers of purple deadnettle poking out from the slightly larger leaves. Unlike henbit, which has smooth flowers, purple deadnettle's flowers are slightly hairy on the outside, with a ring of hairs inside the flower as well.
All three of the lawn weeds are similar. They each have a taproot, or fibrous root system, and are pulled easily from moist to wet soil. Violets creep across the ground, forming a mat, unlike henbit and purple deadnettle, due to its growth of rhizomes, underground stems that root into the ground. The root system of violets may need prying from the ground with the help of a dandelion weeder or kitchen fork if the stems begin to break while being pulled.