Knowing how to identify the leaves of weeds accurately helps you to choose the most effective method of weed control, since no single herbicide or method can control all weeds. You want to identify weeds also because some weeds cause more damage than others to your gardens. Weed species reproduce differently -- some germinate annually in the summer and winter, others like biennials live through two growing seasons, while perennials extend past two years.
Look for weeds with single, long, narrow leaves containing veins that run parallel to each other called monocots. Grass weed, a common monocot variety, features a portion of a larger leaf blade circling the stem at the base of the plant. The grass leaves may be rolled as they come out of the bud shoot, lay flat or rise in a V-shape.
Identify barnyard grass, a summer annual, by smooth leaf blades about 3 to 12 mm wide. Each leaf has a distinct white midvein or main rib of the leaf. Barnyard grass also grows stiffly erect.
Pinpoint crabgrass, a summer annual, by its flat leaves 5 to 10 mm wide covered with soft hair. Some crabgrass lack hair on its leaves and stems. Crabgrass grows in a decumbent way, meaning its tips grow upward but the plant base is broad.
Single out the summer annual, giant foxtail grass weed by how it grows erect to about 3 feet tall with short, hairy leaf blades 10 to 14 mm wide.
Locate Japanese stiltgrass growing in shady areas. This grass weed, also known as Mary's grass, grows up to 3.5 feet tall with asymmetrical leaves, meaning the leaves do not grow the same on each side. Each leaf features a shiny midrib placed off-center that distinctly identifies this weed. Each leaf has a length of 1 to 3 inches and width of 5 to 8 mm.
Identify broadleaf weeds by their wide leaves with net-like veins. When broadleaf weeds seedlings appear, they always have two leaves. As they mature, the leaves appear opposite to one another or alternately on the stem. Broadleaf weeds usually have a leaf stalk called a petiole, although some do not. Leaves may be hairy or smooth.
Recognize the winter annual chickweed by its leaves appearing in pairs in shapes like small eggs to footballs. Mouse-ear chickweed, also called sticky chickweed, features leaves that look like hairy mouse ears growing opposite each other.
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Distinguish dandelion, a perennial weed, by its circular group of leaves coming from the plant's stem at the soil's surface, known as a basal rosette. These leaf rosettes stay green throughout the year. Break a leaf and you will see a milky fluid emerge.
Pick out Japanese clover, a summer annual, by its oblong-shaped leaflets that grow in threes. Each leaflet has a distinct vein running down its center. Attached to the center vein are veins running parallel at 90-degree angles.
Spot the perennial plantain weed by the cluster of leaves growing at ground level. Buckhorn plantain weeds have narrow leaves looking like a 2 to 10-inch long shaft with a pointed head, usually curled. You will see raised veins running parallel underneath each leaf. Broadleaf plantain weeds have wide, egg-shaped leaves from 1.5 to 7 inches long. Several veins run parallel to the edges of the leaves.