Professional Lawn Care
 
 

Keeping weeds at bay

There's something soothing about seeing an even expanse of green grass that seems to lower our blood-pressure a bit. And to some people, when that expanse is broken up by something growing where it shouldn't be growing, it seems to raise it a notch or two. Weeds are just one type of plant that we have decided shouldn't be growing in one particular place. Wild orchids growing in Hawaii are considered weeds there. It's just your point of view as to what makes a weed a weed. Some weed-type plants are very invasive and fast growing. Their growth habit overtakes our cultivated turf plants, depriving them of food and water.

Some common lawn weeds are annuals. Sprouting from seeds, they develop, blossom and form new seeds, then die in the fall, repeating the process each year. Crabgrass is one such weed. Once these types of weeds take root, they are difficult to remove without harming the lawn. The ideal control prevents them from developing. Applying a Pre-emergent Control in the spring does this. The soil's surface is covered with a microscopic protective layer that prevents any germinating seeds from taking hold, including crabgrass. If left undisturbed, this protective layer will maintain its defensive qualities throughout the prime germinating period. This is when most weed seeds will normally start developing. Of course, there is no 100% guarantee that additional seeds won't be carried in by winds, birds, or any number of other methods.

Thoroughly read, understand, and follow all information on herbicide labels. Avoid windy days, as these materials can damage many landscape and garden plants if they drift (spray droplets land off the lawn). Also avoid hot days (over 85 degrees F). It's best to have adequate soil moisture, but no rain for 24 hours after application. Don't mow for a few days before and after application. Consider spot treating weeds rather than broadcasting weed killer over the entire area. Use caution on newly seeded areas; wait four mowings before treating newly seeded lawns and 30 days before seeding areas treated with broadleaf herbicides. Read the label regarding potential tree damage when used on lawns growing over tree root zones.

Weed types:

Bentgrass

Quackgrass and Bentgrass are undesirable perennial grasses that grow as weeds in many lawns. Unfortunately there is no herbicide you can use to kill these two grasses that will not also kill the desirable lawn grasses.

Bentgrass is shallow-rooted. Patches appear as puffy, fine-textured grasses in Kentucky bluegrass lawns. You can remove patches of Bentgrass by cutting the patch out with a hand sod cutter or shovel. Cut down to at least one-inch deep. You will need to reseed the area.

Quackgrass produces many underground stems, called rhizomes, that are almost impossible to remove by digging. Broken pieces of rhizomes left in the soil will sprout to make more Quackgrass plants. One method of controlling Bentgrass and Quackgrass is to apply a herbicide that contains the active ingredient glyphosate. These herbicides are sold as Round Up or Kleen Up. Be aware that glyphosate kills desirable grasses as well as weeds. Apply the herbicide only on the Bentgrass and Quackgrass patches.

For Bentgrass, apply the herbicide to an area about six inches or so outside the patch of Bentgrass to kill the individual stems which are creeping outwards from the patch, otherwise, these patches will reemerge. Whether Bentgrass or Quackgrass, apply glyphosate in spring or fall when the grasses are actively growing. Wait approximately seven days, then reseed or sod the area. If you decide to till the soil prior to establishment, and see bits of Quackgrass rhizomes coming to the surface, remove these. Or wait two weeks or so until enough new Quackgrass leaves emerge and kill the new plants with a second application of glyphosate.

An alternative method is to mow the lawn-wait 3 - 4 days, then wipe the glyphosate onto the taller growing Quackgrass with a paint brush,sponge mop or applicator. Be sure to read and follow label directions.

Bermuda Grass

Bermuda grass is an annual, fine textured "creeping grass" that grows and spreads rapidly during warm summer months. Getting Rid of It: Due to its rapid and sometimes widespread growth during warm months, Bermuda can quickly take over cool-season grasses while dormant. Herbicides are usually not as effective as simply hand-picking these weeds before they grow out of control.

To help prevent this, you can apply a pre-emergence just prior to its growing season (usually spring time) to prevent the seeds from germinating. However, the other extreme is to apply fluazifopbutyl or glyphosate to kill all of the grass, then reseed over it. This is only suggested if you plan on replanting or renovating your lawn afterwards.

Crabgrass

Crabgrass is a warm season annual grass which grows best in the heat of midsummer when desirable lawn grasses are often semi-dormant and offer little or no competition. Crabgrass overwinters as seed, comes up about mid-May or later, and is killed by the first hard frost in fall.

Crabgrass grows best in full sun. It does not grow in shady places. Crabgrass can be controlled in a number of ways, but the best defense against crabgrass is a thick vigorously growing lawn that is mowed no closer than 2-1/2" for cool season grasses.

Fertilize the lawn in late summer or fall and again in spring to develop a dense, healthy stand of grass. Fertilized bluegrass does not go into midsummer dormancy as soon as unfertilized bluegrass. Pre-emergent applications made when soil temperature are still below 60 are the best prevention. Not recommended for areas where new grass seed is going to be planted during the first half of the growing season. Applications lose their effectiveness if the lawn is raked or disturbed during the first half of the growing season.

Postemergence crabgrass herbicides are now available. These are products that are applied after the crabgrass seed has sprouted. The herbicide (ACCLAIM) gives excellent crabgrass control with one application. This product should be applied when crabgrass is in the 3 to 4 leaf stage of development.

Dallis Grass

Dallis grass is a perennial grass with light-green color. Dallis is easily identified by its long seed-heads that protrude from the top. Dallis tends to thrive in wet areas with lots of heat, and grows in circles out from the center of the weed. Try to improve the drainage of your lawn to take dampness away from the areas were they grow. Additionally, allow the top of the soil to partially dry between each watering to help retain the water only in the root area. Apply pre-emergence fertilizers ( usually in the late-spring ) to prevent seed germination and growth. Once weeds are established, pull them by hand and make sure you get the roots as well. After pulling, reseed the area with the desired grass.

Dandelions

Broadleaf weed. Best treated during active growing cycle with a spot treatment. If you use a dry granular form of weed killer or a weed and feed type of fertilizer, apply it to wet grass and weeds. The weed control material must stick to the leaves of the weed plants to be effective. If you spray a liquid, apply it only on a calm day so material will not drift onto desirable plants.

Remember, broadleaf weed killers are broadleaf plant killers. They do not, for example, differentiate between dandelions and tomato plants. Apply them only to weeds in the lawn. Be careful not to get the material onto desirable plants in your yard. Read and follow all label directions.

Ground Ivy


Ground ivy is hard to control because you can't pull it out easily in lawns and many commercial broadleaf lawn weed killers have little or no effect on it. The most common active ingredient in granular and liquid broadleaf lawn weed killers is 2,4-D, but 2,4-D has little effect on ground ivy. Another common active ingredient, MCPP, or, mecoprop, also has little effect on ground ivy. Dicamba is an active ingredient that does control ground ivy. Dicamba is also called Banvel.

There are several lawn weed killer products available that contain dicamba. Most of them also contain 2,4-D and MCPP. However, you may still need to make repeat applications with dicamba-containing products to completely control ground ivy. Ground ivy spreads via creeping stems that propagate new plants.

Moss

Moss does not develop in healthy lawns. Lack of fertility, soil compaction, poor drainage, shade and poor soil aeration are the most common cause of moss in lawns. Moss is not directly harmful to grass, but moves into bare spots in the lawn as the grass thins out. Lime has often been suggested for moss control. Lime will raise the soil pH but will do little or nothing to prevent moss growth. The fact that the soil is acidic has little to do with the growth of moss. In fact, we see moss growing on limestone and concrete. If your lawn area is moist and shady, you will have difficulty controlling moss because you have an ideal environment for moss growth. Moss is often troublesome in spring when temperature are cool and soil moisture high.

Mushrooms

Mushrooms, also called toadstools or puffballs, are fruiting bodies of soil fungi. They appear in lawns during wet weather in spring and summer. Mushrooms live on organic matter such as roots, stumps and boards in the soil. Most don't harm the lawn but are unsightly. Mushrooms that grow in arcs or circles of dark green grass are called fairy rings. The arcs or rings enlarge from 3" - 2' each season as the fungi grows outward. The fairy ring fungus may interfere with water flow through the soil and stress the lawn.

There is no chemical control for mushrooms. Time is the best cure. Once the buried wood has completely decayed the mushrooms will disappear. Break mushrooms with a garden rake or lawn mower for temporary control. This helps to dry the mushrooms and reduces the risk of children eating them. Control individual mushrooms by removing the organic matter. Dig up and remove the wood. Fill and reseed, or sod, as needed.

Nimblewill

A warm-season perennial found throughout North America east of the Rockies. Invades cool-season grasses by seed or stems. It has shallow roots.

Thick sod reduces the opportunity for it to take hold, however, in thin areas, or surrounding garden beds, it can quickly spread into lawn areas. Remove the plants by pulling out by hand. Nimblewill sets seeds in early fall; then lay dormant until next spring.

Once it takes hold there is no selective control for removing it from the lawn. Must use a non-selective herbicide that will kill all plants, then reseed area.

Plantain


Broadleaf plantain is a common broadleaf weed in lawns. See treatment and description for dandelions.

Quackgrass

(See Bentgrass)