How do I get rid of weeds in my lawn without killing the grass?

Start with the least drastic tool that works. Pull scattered weeds by hand after a rain, spot-treat the rest with a selective herbicide that names both your grass and the weed on its label, and spray only while the weeds are actively growing. Then fix the reason they got in, which is usually thin grass. Virginia Cooperative Extension's lawn guide traces most weed problems in Virginia to a single mistake: mowing the lawn too short.^[1]

Know what you are fighting first

Two identifications decide everything else: your grass and the weed.

Most Virginia lawns are tall fescue, sometimes mixed with Kentucky bluegrass. Warmer parts of the state also have bermudagrass and zoysiagrass lawns. That matters because a herbicide that is safe on one grass can badly injure another, so you cannot pick a product until you know which you have.

Weeds fall into two broad groups. Grassy weeds, such as crabgrass and wiregrass, look like grass. Broadleaf weeds, such as dandelion, clover, chickweed and henbit, have wider leaves and usually flowers. Each group is also either annual, living one season and returning from seed, or perennial, coming back from the same roots year after year. Some annuals die off on their own in summer heat or winter cold within a few weeks, and those may not need treating at all. Your county's Extension office can help name a weed you cannot identify.

Pull by hand where you can

Hand-pulling is underrated. Hand-pulling is easiest on weeds with few or no creeping stems, such as dandelion, plantain, crabgrass and goosegrass, and harder on creepers such as bermudagrass, nimblewill and white clover.^[1] Pull the day after a rain or a deep watering, when roots let go more easily,^[1] and use a long-handled weeding tool to get as much of a dandelion's taproot as you can.

Bag what you pull. pulled plants left on the lawn can keep growing long enough to drop seed, and stem pieces of some weeds root again.^[1] For a lawn with a few dozen weeds, an hour with a weeder often beats a trip to the store.

Use a selective herbicide the right way

A selective herbicide kills certain plants and spares others. Of the 33 active ingredients sold in consumer lawn weed products, 25 do not harm cool-season grass.^[1] The common homeowner broadleaf killers, 2,4-D, MCPP, MCPA, dicamba, triclopyr and carfentrazone, kill broadleaf weeds without harming the turfgrass when used as labeled.^[2] Look for those names in the active ingredients list rather than on the front of the bottle.

Read the whole label before you buy. Using a pesticide in a way its label does not allow violates federal law; the label is the law.^[5] It tells you which grasses the product is safe on, which weeds it controls, how much to use and how long to wait before reseeding. Dicamba can move a short distance through soil and be taken up by the roots of nearby trees and shrubs,^[2] so give ornamental beds a wide margin.

Some weeds take more than one round. Ground ivy, wild violet, common lespedeza, wood sorrel and Virginia buttonweed are hard to kill; products with triclopyr or penoxsulam work best, and expect to treat them more than once.^[1] Ready-to-use sprays have a shorter shelf life than concentrates, so pass on any bottle that has sat on a store shelf for more than six months.^[1]

Timing is half the job

Weeds have to be actively growing for a postemergence herbicide to work: 50°F or warmer for cool-season weeds and about 80°F or warmer for warm-season weeds.^[3] Spraying a drought-stressed or half-frozen weed mostly wastes product.

Annual broadleaf weeds are easiest to kill while young, and perennial broadleaf weeds are best treated in fall, when they are moving food down to their roots for winter.^[1] Henrico County's Extension office suggests treating summer annuals such as spurge and lespedeza in April and May, and winter annuals such as henbit, bittercress and chickweed in October and November.^[2]

Weather on the day matters too. Skip spraying when wind is above about five miles per hour,^[1] and do not treat soggy ground, because a rain on saturated soil can carry herbicide off in runoff to storm drains.^[1] Most herbicides are rain-fast within four to eight hours,^[1] and you should keep foot traffic off the treated area until rain or irrigation has washed it in, so it is not tracked onto other plants.^[1] A spray takes one to three weeks to finish the job,^[1] so resist the urge to spray again after two days.

What about natural weed killers?

Most vinegar, citric acid, clove oil and soap weed killers are nonselective: they brown the grass along with the weed, and the grass and mature weeds both recover in one to two weeks.^[1] They are better suited to seedlings in beds and walkway cracks than to lawns. Iron HEDTA products are one organic option that selectively controls or suppresses broadleaf weeds in turf.^[1]

Make the grass do the work

Herbicides clear weeds; grass keeps them out. High-quality lawn grass kills seedling weeds and prevents large weed stands,^[1] so every gap you close is one less weed next year.

• Mow higher. Mow tall fescue at 3 to 4 inches,^[1] and see what height to mow fescue for the details.
• Feed in fall. Cool-season lawns do best fed from late summer into November; see when to fertilize a Virginia lawn.
• Fill bare spots. Overseed thin areas in fall, and plan weed control around it: most broadleaf herbicides cannot be used on young grass seedlings, and herbicides may typically go on new turf after the second mowing, with exceptions, so follow the label.^[4][1]
• Fix the soil. Test the soil every three to four years and keep the pH between 6.3 and 6.8.^[1]

If grassy weeds are your main problem, our guide to why a lawn fills with crabgrass covers prevention timing.

Stop and call a pro if

• Weeds cover a third of the lawn or more. Killing that much leaves bare soil, and a renovation with reseeding is usually the better plan.
• You cannot identify the weed or your grass, or a product has already damaged the lawn.
• The yard drains to a creek, pond or well, or children and pets use it constantly and you would rather someone trained handles the products.
• Wiregrass or another perennial grassy weed is spreading through fescue. Selective control takes repeated, carefully timed treatments.

If you hire the spraying out, check the company's state credentials first; see what licence a lawn care company needs. Browse more lawn and landscaping answers, compare fertilization and weed control services, or find lawn and landscaping businesses around Blacksburg. To hand the job off, describe your lawn once and local businesses quote it.