Intervene now to control lawn weeds

Right now is the perfect time to control weeds in lawns. The cold, rainy weather has slowed the growth of weeds and that can delay the germination of summer weed seeds.

//

Next week, I will discuss using pre-emergent herbicides to control summer weeds. But now we need to look at the weeds that are in our lawns to determine the best way to control them.

There are several weeds that can be hard to control, but with proper turfgrass management we can reduce the weeds.

However, there are times when it becomes necessary to use herbicides. Some of the weeds that are difficult to control are dandelion, wild garlic and onion. Also, some lawns have a sticky weed that needs to be controlled now.

As a kid, we loved to play with the seed head of dandelions by carefully breaking the stem of the plant and blowing the puffball at the end of the stalk. The seeds would float away on the wind. Little did we know that we were seeding the neighbor's yard.

Dandelion is a winter perennial that grows back from a taproot. However, the plant can be propagated from seed.

Dandelion leaves form a rosette close to the ground. This growth habit makes it hard to control by mowing. Digging this weed is possible, but if any part of the tap root is left the plant will grow back.

One way to tell dandelion from other weeds is that the leaves and stalk of the plant will exude a milky substance when broken.

Dandelion is one of the hardest weeds to control in lawns, especially centipede and St. Augustine lawns. The deep taproot stores lots of energy, which allows the plant to come back after herbicide applications. Use herbicides that contain 2,4-D. It is found in many products, usually in conjunction with MCPP and dicamba. It will take at least two applications to control dandelion.

In centipede and St. Augustine, these products must be used at a half rate or it can injure the turf. Atrazine, which is commonly used in centipede and St. Augustine, will give fair control at best.

The next group of hard-to-control weeds is wild garlic and onion. Wild garlic (Allium vineale) and wild onion (Allium canadense) are winter perennials, with wild garlic the more common of the two. These weeds emerge in late fall from underground bulbs and grow through the winter and spring. In late spring, they form aerial bulblets and the plants die back in early summer. The underground bulbs can persist in the soil for several years.

Both have thin, green, waxy leaves. Those of wild garlic are round and hollow, while those of wild onion are flat and solid. This is the best way to distinguish between them, because they have the same odor.

This is a great time to hand pull these weeds, because the soil is so soft. I cleaned up a section of my lawn this way. It took me two to three years, but the amount of wild garlic and onion is greatly reduced.

There are a number of herbicides that will control these weeds. Imazaquin, the active ingredient in Image Nutsedge Killer, will provide control for wild garlic and wild onion. This product should not be applied to warm-season turf during green-up in spring. Three-way broadleaf herbicides containing 2,4-D, dicamba and mecoprop will provide control of wild garlic and wild onion with repeat applications. These products can be used safely on most turfgrasses, but reduced rates are recommended when applying to St. Augustine or centipede grasses. Apply during November, very early spring, and again the next November for best control. Do not apply these herbicides during the spring green-up of warm season turfgrasses, or over the root zone of nearby ornamental trees and shrubs.

There is nothing worse than running barefoot through your lawn and getting stickers in your feet. These stickers are from a low-growing, mat-forming weed called lawn burweed. It is a winter annual that comes back from seed each year. The seeds are the stickers.

One of the best ways to control this weed is to have a thick, healthy lawn. The thick lawn out-competes the weeds for sunlight, water and nutrients.

Apply herbicide in late fall and early winter. By mid-March, the seeds are starting to harden, and killing the weed will still leave the sticker.

Again, the three-way products will control this weed, and they will usually control it with one application. For centipede and St. Augustine, use atrazine.

It takes herbicides longer to work in cold weather, so wait two to three weeks before expecting to see weeds dying.

Charles Phillips is a retired Columbia County Extension Service agent and operates Hort Consulting. He can be reached at cphillipshort@comcast.net.