Even experienced gardeners occasionally have trouble distinguishing between an unfamiliar species of weed and useful plants that “volunteer” to grow in the garden or lawn. Certain weeds produce broad, flat leaves that look for all the world like the foliage of a corn plant (Zea mays), which grows in U.S. Department of Agriculture plant hardiness zones 4 through 8. You might have to inspect the plant more closely or wait until it blooms to determine that it is, in fact, a weed and not the product of a stray corn kernel dropped by a bird or squirrel.
Giant reed, Johnson grass and quack grass can spread rapidly and overwhelm other vegetation in the yard and garden. They compete with desirable vegetation for nutrients and water. Glyphosate is a nonselective, systemic herbicide that kills all three of these weeds. You can spray a ready-to-use glyphosate herbicide in a coarse, narrow stream onto the foliage of the weeds. For large stands of weeds, a broader stream of herbicide may be used. Try to spray on windless days so the herbicide does not drift onto desirable plants and kill them. Wet the weeds’ foliage, but not to the point of runoff.
Johnson grass (Sorghum halepense), a perennial grassy weed, has stalks that grow 6 to 7 feet tall with a clumping habit. The weed is a pest in every USDA zone, growing in all contiguous states except Maine. Johnson grass can often be found in riparian areas, but will grow happily in the middle of cotton fields, in vineyards, orchards and vegetable gardens. When the plant is young, it looks like a small corn seedling. To positively identify the weed, carefully dislodge it from the soil. Unlike corn, Johnson grass will have an oval, red-brown to black seed attached to the roots. The leaves have smooth edges and a middle vein that is off-white at its base. Johnson grass also produces flowers between May and October.
Growing up to 20 feet tall, the giant reed (Arundo donax L.) also produces stems that look like cornstalks. The leaves are long and lance-shaped, like corn’s, and the hollow stems are used to make reeds for musical instruments. Giant reed has a clumping habit and thrives in warm areas, especially where the environment is wet, such as ditches and around ponds and streams. It grows best in USDA zones 6 through 11. In late summer, giant reed produces a purplish to silver colored plume up to 2 feet long that rises above the foliage.
Quack grass (Elytrigia repens) is a cool-season, perennial member of the grass family. It prefers to grow in moist sites and disturbed areas, but is just as happy growing in the garden. The grass grows from rhizomes below ground and produces flat, droopy leaves about 1 foot long. Unlike corn plants, quack grass has leaves with a waxy underside and a hairy or waxy upper surface. Quack grass also has a clumping habit and can grow around 4 feet tall. In summer, quack grass produces spiked flowers up to 8 inches long. Seeds appear in spikelets along the seed head.
How it Spreads:
How it Spreads:
How it Spreads: