Green foxtail (Setaria viridis) is an aggressive grower and is a problem when competing with vegetable crops. Adjustments to lawn care practices, including frequent watering and keeping grass cut short, can help control the spread of this weed. A pre-emergent herbicide is recommended and because germination continues throughout the season, subsequent treatments may be necessary.
Orange hawkweed (Hieracium aurantiacum L.) quickly forms mats of hairy stems with orange or yellow flowers. One shallow-rooted plant can grow to cover as much as three feet of turf in one year and aggressively competes for soil nutrition, space and sunlight. Hand-pulling plants by the roots is recommended. Regular mowing of lawns helps to reduce flowering and seed distribution of this invasive weed.
Dodder (genus Cuscuta) is a parasitic plant with many species affecting ornamentals, crops and native trees. Sprouting from seed, dodder latches onto a host plant. Delayed spring planting can bypass the window of opportunity for developing dodder. Dodder-resistant plants may also be selected for cultivation. Hand weeding is effective and herbicides may be used to treat sites where dodder is likely to develop.
Common ragweed (Ambrosia artemisiifolia), is a prolific pollen producer and is the primary cause of hay fever during summer months. Treatment of ragweed with herbicides can be challenging, because some varieties have developed a resistance to these chemicals. Hand pulling is an effective management strategy. Regular mowing will also help to limit the growth of this ubiquitous weed.
Native to the Eastern half of the United States, deer-tongue grass (Dichanthelium clandestinum), thrives in moist, sandy soil. With stems reaching nearly five feet tall, this clump-forming perennial is recognized by smooth, pointed leaves, said to resemble the tongue of a deer. Flowering form in summer months, usually fully sheathed by leaves.
Bull Thistle (Cirsium vulgare) grows two- to six-foot tall prickly plants that produce vibrant purple flower heads in late summer. Hundreds of seeds are attached to light hairs which carry easily on wind to distribute new growth. Existing plants may be removed using a shovel and new growth inhibited by regular mowing while thistle is still small to prevent flowering seeds. If necessary, chemical treatment should be applied in late fall.
Commonly used as forage grass, smooth brome (Bromus inermis) is hardy and trample resistant. Also used along roadways to inhibit soil erosion, it has continued value as a cultivated grass, but its tendency to spread quickly and uncontrolled makes smooth brome a threat to lawns, grasslands and forests. Smooth brome can be controlled through chemical treatment. Herbicides should be employed in late fall after first frost for best results.
A perennial with slender stems and short rhizomes, slender rush (Juncus tenuis) can thrive in shaded areas and in heavily compacted soils, making its clumped growth a common sight along walking paths, driveways and suburban lawns. Although small and sometimes overlooked early in the season, slender rush spreads easily and can become invasive. Hand weeding is usually necessary to control problems with slender rush.
Spotted knapweed (Centaurea stoebe), a perennial weed, reproduces by seed spread by wind, water or animals and displays grayish foliage with purple flowers blooming in late summer. The noxious weed is dangerous to other plants and a skin irritant when touched. Spread can be reduced through mowing to prevent seed development and through hand pulling of established weeds. Herbicides are effective in controlling spotted knapweed, but may damage or kill related plants.
Tall fescue (Festuca arundinacea) is a cool-weather grass, but is tolerant of hot weather and drought conditions. Reproducing by seed, tall fescue grows in clumps with vertical leaves that are difficult to eradicate once set, as the density of tall fescue growth will eventually out-compete native species. In some cases, controlled burning has been employed to eradicate invasive tall fescue. Chemical treatment is also effective in management of invasive tall fescue.
Originally: 10 Types of Weeds