Weeds and Your Lawn

Know Your Lawn

Before making any weed management decisions, sketch a map of your property and locate any problem areas.

lawn diagram
Smooth Crabgrass -- an annual warm-season weed found throughout the United States and Canada. Flowers resemble the digits on a hand. Germinates in several flushes throughtout the late spring and summer.

Plant the Proper Grasses

Base your selection of turfgrass mixture on intended use of the turf, climate, and availability of light and irrigation. In New York State, cool-season grasses, such as Kentucky bluegrass, fine and tall fescues, and perennial ryegrass generally grow best. Choose a good-quality seed mixture of species that are well adapted to the soil conditions at your site. In shady, moist, or acid conditions, other groundcover perennials might be a better choice than grass.

Ground ivy -- a perennial weed with long, creeping, square stems that root at the nodes. Rounded leaves have toothed margins. Forms dense prostrate patches, especially in damp, shady areas.
ground ivy


speedwell Slender speedwell -- a creeping perennial weed with attractive blue flowers in the spring and small round leaves with scalloped margins. Reproduces in Northeast primarily by underground stems. Plants remain green year-round.


Prostrate knotweed -- a summer annual weed that trails along the ground with branching stems and small leaves. Reproduces by seed, and is one of the first summer annuals to emerge. Plants form a tough, wiry mat in areas of low fertility and in compacted or other stressed sites.
knotweed

Determine Your Weed Tolerance

Personal values, uses of the site, and level of maintenance will dictate the quantity of weeds you permit at a specific site. Focus your management strategy on weeds that you cannot tolerate. Some homeowners enjoy wildflowers in their lawns. You can purchase low-maintenance blends of grasses, violets, clovers, yarrows, and other flowers that thrive on biweekly mowing from a variety of seed sources. (See Resources.)

White clover -- a common perennial weed that reproduces by creeping stolons and seeds. Stems are prostrate, leaves are in threes, and flowers are pinkish white and fragrant.


Broadleaf plantain -- a perennial weed found in all turf conditions. Has broad oval leaves with parallel venation. Reproduces by seed and forms a short taproot.

Mow, Fertilize, Irrigate

Mow regularly at the appropriate height to minimize weed pressure. In New York State, an ideal mowing height for most grasses is 3 inches. Mowing often and at the optimal height encourages healthy growth and deep rooting of grasses. Most weeds cannot tolerate frequent mowing.

Apply a balanced fertilizer two weeks after the last mowing in the fall to optimize hardiness and spring greening. Never apply fertilizer after the ground is frozen; it is likely to run off. Around Memorial Day, you can apply a smaller amount of fertilizer, if it is needed. Before you select a fertilizer, have your soil tested to determine your lawn's specific fertilization needs. Also, test the pH of your soil; most grasses do best in neutral to slightly acid soil (with a pH of 6.5 - 7.0).

Most lawns do not need to be watered regularly. Cool season grasses can survive with as little as 1/4 inch of water every three weeks. Inappropriate watering -- either too much or too little -- weakens the grass and makes it more susceptible to weed problems.

Managing Weeds Are Herbicides Really Necessary?

Identify which weed species are present before selecting a management strategy. Most weeds are not problematic, while others can be invasive. Your best strategy to prevent a weed invasion is to maintain a healthy lawn.

In areas where the turf is thin, overseeding (planting new seed on an existing lawn) will help grasses out-compete weeds. Prepare the area to be seeded with close mowing or aerification to expose or loosen soil, and ensure that seeds and soil make contact. Irrigate to aid early development. Consider fertilizing once grasses are established.

Remove sources of weed seeds. Many weed problems occur as a result of seeds drifting from adjacent sites as well as from weeds already present in the lawn. Thistle and millet seed bird feeders are a frequent source of these weeds.

Many weeds can be controlled with herbicides during early development, while some are more easily pulled by hand. Many hand tools exist for removing specific weeds.

Susceptibility to herbicides varies considerably and most weeds are better managed by spring and fall applications. Check the Cornell Guidelines for management strategies or the names of herbicides that will be effective for the weed species present at your site. Time, money, and product will be wasted if herbicides are used improperly.

Dandelion -- a perennial composite weed that reproduces by wind-blown seed and is easily recognized by its bright yellow flowers in late spring and summer.

Are Herbicides Really Necessary?

Before using herbicides consider the following:

Effectiveness-
Environment-
Economics-

References

Resources

"Resources are provided for informational purposes and do not constitute anendorsement by Cornell University, Cornell Cooperative Extension, or the New York State IPM Program."

From: The New York State IPM Program. NYS Integrated Pest Management Program, NYSAES, Geneva, NY 14456

Authors: Jana Lamboy, Leslie Weston and Frank Rossi

Photos: Robert McNiel and Joe Ogrodnick.

For more IPM for lawns see UConn's Turfgrass IPM site.

Information on our site was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate.

The information in this material is for educational purposes. The recommendations contained are based on the best available knowledge at the time of printing. Any reference to commercial products, trade or brand names is for information only, and no endorsement or approval is intended. The Cooperative Extension system does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which also may be available.All agrochemicals/pesticides listed are registered for suggested uses in accordance with federal and Connecticut state laws and regulations as of the date of printing. If the information does not agree with current labeling, follow the label instructions. The label is the law.Warning! Agrochemicals/pesticides are dangerous. Read and follow all instructions and safety precautions on labels. Carefully handle and store agrochemicals/pesticides in originally labeled containers immediately in a safe manner and place. Contact the Connecticut Department of Environmental Protection for current regulations.The user of this information assumes all risks for personal injury or property damage.Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Kirklyn M. Kerr, Director, Cooperative Extension System, The University of Connecticut, Storrs. The Connecticut Cooperative Extension System offers its programs to persons regardless of race, color, national origin, sex, age or disability and is an equal opportunity employer.

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