Field bindweed (Convolvulus arvensis) in flower.

Field bindweed (Convolvulus arvensis) in flower. Credit: Howard F. Schwartz/Colorado State University/Bugwood.org/Colorado State University/Bugwoo

DEAR JESSICA: Are there any products that will kill bindweed, dallisgrass and nut grass?-- John Rogo, Glen Cove

DEAR JOHN: Bindweed comes in field and hedge varieties, and they are invasive vining weeds similar to morning glories, except they're perennial and they have a very deep root system that runs both vertically and horizontally, which makes it very difficult to control.

Cultivating or turning over the soil occasionally will do more harm than good, as disturbing the roots breaks them and spreads them around, leading to more weeds. But if you go gangbusters on it and cultivate the soil repeatedly and regularly, you will have a fighting chance against it because you'll constantly be dragging the roots up to the surface, where they'll dry out and die. This takes dedication. Doing so halfheartedly is worse than doing nothing, and missing just one regular cultivating session can reverse months of work.

Till the soil within a week of the appearance of new weeds and then repeat at least once a week until no new weeds appear. The regimen will need to be kept up during the entire growing season, and possibly for several years. Be aware that missing just one tilling can reverse all your efforts, as the plant will take advantage of its freedom.

Tilling isn't practical, of course, if the weed has invaded your lawn, as you'd be throwing out the proverbial baby with the bathwater. Fortunately, bindweed usually isn't a problem in lawns because grass is the one plant that can choke it out. If bindweed is growing in your lawn, work on improving turf health and density, and the bindweed should die off on its own. In other areas, broadleaf weed killers may help if applied in early spring and fall following package directions.

Dallisgrass is a clump-forming perennial weed that looks like grass, only taller, but sends up a thin branched seed head. Control can be attained by digging out new plants before their roots become established and before they set seed. Mature plants also can be dug up, but if you leave behind a small piece of root, it may grow back.

Seeds also can hitch rides on lawn mowers, so if your grass is cut by a service or if you're using your lawn mower to cut both affected and unaffected areas of lawn, contamination is a concern. Seeds that drop on exposed soil will germinate and spawn new weeds, so apply grass seed to fill in bare patches in the lawn. Then, in late winter or early spring, apply a pre-emergent crabgrass killer to the affected area to prevent germination of overwintered dallisgrass seeds.

Dallisgrass (Paspalum dilatatum) weed

Dallisgrass (Paspalum dilatatum) weed Credit: John D. Byrd/Mississippi State University/Bugwood.org/Mississippi State University/ Bugwood.org

Glyphosate, the nonselective herbicidal ingredient in Round-Up, is effective against active dallisgrass, but because "nonselective" means that it will kill whatever it comes into contact with, spraying weeds in your lawn will kill the grass, too. If you choose to go this route -- and it should be a last resort -- try to direct the product only on the weed, and then reseed areas where grass has died.

Nut grass, also called nutsedge, unfortunately, is listed as the worst weed known to man in "The World's Worst Weeds: Distribution and Biology" (Krieger Publishing, 1991). It is considered a noxious weed in more than 100 countries, spreading via seeds, tubers and rhizomes.

Because it roots so deeply, nutsedge is very difficult to remove. To eradicate it, it's important to cultivate very, very deeply, as the tuber system runs quite deep. Each plant can produce hundreds -- even thousands -- of tubers in one season, some of which can remain dormant in soil for 50 years, according to a Cornell Cooperative Extension horticultural fact sheet. And it's even more prolific after a wet spring.

SedgeHammer, a selective herbicide that targets the weed without threatening the grass, is by far the most effective product registered for use against nutsedge on Long Island. It can be applied at this time of year, but you should call a landscaper who is a certified pesticide applicator to handle the job.

Yellow nutsedge, also known as nutgrass. (June 20, 2006)

Yellow nutsedge, also known as nutgrass. (June 20, 2006) Credit: Newsday/Ken Spencer

DEAR JESSICA: I can't make out whether this small tree growing in my yard is a white flowering dogwood or a crabapple. Hope you can help me. -- Gloria Boccio, Orient

DEAR GLORIA: Your leaf certainly didn't come from a dogwood. The serrated edges are a dead giveaway; dogwoods have untoothed leaves with veins that curve toward the center. Without seeing the entire tree, I can't be 100 percent sure, but the leaf you sent does look like it belongs to a crabapple.

 

 

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