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NCSU Extension Publication:AG-763W
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Summer Weed Control - General

Weed types

Broadleaf - Leaves are generally wide, and have net-like veins. Broadleaf plants have round or square stems and leaf shapes vary (round, heart, oval or linear arrangements). Leaves are typically found in clusters or bunches with one or more leaflets. Growth habits include upright, vining, rosette, and spreading. Generally broadleaf weeds have showy flowers. Summer annual broadleaf weeds emerge in the spring or early summer, grow during the summer, and produce seed in mid- to late summer. Midsummer rains frequently encourage germination. Perennial broadleaf turf weeds are capable of living more than two years. They primarily spread by seed produced in the spring or early summer. Many are capable of vegetative reproduction, which makes them difficult to control.

Grassy - typically upright, bunching plants with fibrous roots. Their hollow stems are either round or flattened. Leaves have parallel veins, are in groups of two, and are much longer than they are wide. Weedy grasses are classified as summer annuals, winter annuals, and perennials. Annuals complete their life cycles in one season by flowering, maturing seed, and dying. Summer annuals germinate from late March through July, depending on the location. They flower in the summer and either die in the fall or are killed by frost. Perennials live more than two years and may produce seed each season.

Sedges - are weeds that resemble grasses but unlike grasses, sedges have three-sided or triangular stems.

Preemergent or Postemergent control?

Preemergent herbicides offer a great option for select annual grass and broadleaf weed control in warm- and cool-season turfgrasses. Since these herbicides control susceptible weed species as they grow through the herbicide treated zone, the herbicide barrier must be established prior to the weed seed germination. In most areas in NC, this occurs in mid- to late-March. Preemergent herbicides are commonly used for crabgrass and goosegrass control but also control other select grass and broadleaf weeds that are propagated from seed. Specifically, with preemergent herbicides, application timing, application coverage, and single versus split applications among other variables are crucial to the results obtained.

Postemergent herbicides for summer weeds usually need to be applied April through June as younger plants are generally easier to control. Herbicides do not control weed seeds they control weed seedlings.Even if you get good kill of top growth, if the plant has already produced seed, the weeds have already ensured future survival for years to come.

HOWEVER!

Positive identification of the specific weed and knowledge of the kind of turfgrass being treated is CRITICAL, or, you could end up with a dead lawn!

Additionally, read and carefully follow all label instructions including the specific kind of weeds controlled and any restrictions on where materials can be applied!

For more information go to:

www.TurfFiles.ncsu.edu