How to win the weed war
In flower beds, pull crabgrass before it sets seed. To thwart crabgrass in lawns, keep the turf well fertilized and vigorous, so it will provide tough competition for weeds. Also water your lawn deeply, but infrequently; this tactic will dry out crabgrass roots, killing the weeds or at least diminishing their vigor. Solarization can control crabgrass if high temperatures are achieved.
Use corn gluten as a preemergence treatment. If chemical control is necessary, in ornamental beds only, use a postemergence herbicide control that kills grasses.
Pulling usually doesn't eradicate it ― the stems break off, but the weed returns from the roots. To control its spread, you'll have to dig the roots out repeatedly (persistence is required). It's important not to let bindweed set seed, since the hard-coated seeds can sprout after lying dormant for 50 years!
Best control is prevention. Remove flowers before they set seed, and pull or hoe seedlings. Kill established plants by regularly cutting to the ground any stems that have reached six inches tall.
For chemical control, in midsummer, when bindweed is at the height of its growth season but has not yet set seed, spot-treat isolated patches with glyphosate.
If you have a Bermuda grass lawn, use an 8-inch deep barrier or edging to prevent it from advancing into other parts of the garden. Dig up stray clumps before they form sod, being sure to remove all the underground stems; any left behind can start new shoots.
Repeated pulling and digging are generally necessary to stop this weed; mulches will slow it down, but it eventually grows through most of them. For chemical control, use a selective postemergence herbicide.
Prevention is the best control. Hoe or pull young seedlings early, before they bloom and set seed. Apply a 1-inch layer of fine mulch to suppress germination in garden beds.
A vigorous, well-fertilized lawn competes well against spotted spurge. If chemical control is necessary in lawns, use a preemergence product in late winter before seeds germinate, following label directions.
Spot treat spurge plants with herbicidal soap when they are young. For spurge growing in cracks in pavement, use a hand weeder.
Hoe or pull nutsedge when it's young and still small ― when plants have fewer than five leaves or are less than 6 inches tall. Older, taller plants are mature enough to produce tubers; when you dig or pull the plant, the tubers remain in the soil to sprout. Repeatedly removing top growth eventually weakens tubers.
For small patches in lawns, dig deeply (8 inches); remove the whole patch, then refill with soil and seed or sod the patch.
Seedlings start out from a single taproot, which soon develops into a shallow, spreading, knitted root system. Tiny yellow flowers are followed by elongated capsules that can shoot seeds as far as 6 feet.
Dig out small plants early. If you have a lawn, keep it vigorous to provide competition; water deeply but infrequently, since frequent light watering encourages this shallow-rooted weed.
You can also use a preemergence herbicide on turf and around ornamentals listed on the label. Spot-treat oxalis in garden areas with glyphosate.
A healthy lawn can outcompete dandelions, so thicken the turf by overseeding and by proper fertilizing, watering, and mowing.
Pull dandelions while they're small, before they produce a taproot and set seed. Once the taproot has formed, you must remove all of it, since new plants can sprout from even a small piece. A dandelion weeder with a forked blade is helpful, or use a hand weeder with a bent shaft.
For chemical control, use a selective postemergence herbicide labeled for dandelions in turf.
To reduce infestations in lawns, keep the turf thick through consistent fertilizing; aerating will help, too. Dig out plantains before they set seed. Be sure to remove as much of the roots as possible (a dandelion weeder is helpful here), since these weeds can regrow from any pieces of the rootstalk that remain.
For chemical control, use a preemergence product or spot-treat plantains in the garden with glyphosate, taking care not to get the chemical on desirable plants.
Hoe or pull these weeds when they're young. Mature plants have a long, tough taproot that is difficult to extract from the soil, and they are of course more likely to have set seed.
For chemical control, use a preemergence herbicide to prevent seedlings from becoming established in lawns and around ornamentals.
Poison ivy looks similar; it's common east of the Rockies and also grows in eastern Oregon and eastern Washington. Usually found in shady areas and at the edges of woodlands, it sprawls along the ground until it finds something to climb, then becomes a vine.
A resin on both poison oak and poison ivy causes severe contact dermatitis in most people. Control the both with an appropriately labeled herbicide, such as glyphosate (be sure to avoid getting these chemicals on other plants).
Pull young plants in spring, before they develop a perennial root system. To kill established clumps, repeatedly prune back the stems as they sprout; this eventually exhausts the roots. Or mow the tops and dig out the roots; repeat the process as new canes grow from roots left behind.
You can also cut stems to the ground and apply glyphosate to the stubs as soon as possible after cutting. Spot-treat any new shoots with glyphosate as they appear.
For best control of small infestations, hoe or dig plants before they can set seed, cutting below the crown to prevent regrowth. Once you've removed puncture vine growing in lawns, improve the soil with compost and sow grass seed in bare spots to prevent the weeds from reestablishing.
For chemical control, preemergence herbicides containing trifluralin may be used on some lawn grasses and ornamentals in late winter or early spring. For postemergence control in lawns, use a selective herbicide.
It thrives in moist conditions but can withstand considerable drought. Its fleshy, dark green leaves are edible, with a tart, lemony flavor.
Purslane is easy to pull or hoe. But pieces of stem can reroot readily, so be sure to remove them from the garden. Also remove plants that have begun to flower, since they can ripen seed even after they've been pulled. Don't compost any part of the plant.
Purslane can also be naturally controlled with solarization.
Thoroughly dig the area and remove all visible pieces of rhizome; this will slow the weed's growth for a few years. You can also suppress quack grass by smothering it; leave the cover in place for at least a year.
For chemical control, use preemergence herbicides on turf grasses and around ornamentals listed on the label. Or spot treat with an herbicide containing glyphosate, taking care to avoid contact with desirable plants.