Q: We sprayed weeds in our lawn with weedkiller and killed them, but a lot of grass died, too. We used a product that was not supposed to kill grass, so what can we do to fix this?
A: First, let's make sure you do not do this again. There are chemicals that kill all plants on contact, and some even sterilize the soil so no new plants can grow for a while. Even though it may seem obvious, these plant killers will kill the good plants in flowerbeds and on the lawn. Sometimes they kill lawn grass even with very low doses.
Be very careful when using them. Do not use them on windy days, and be sure to spray close to the plant so mist will not spread and hit other plants. It is best to use a separate spray bottle or spreader for this type of chemical. Washing the sprayer out several times very thoroughly with soap and water will reduce the risk of problems but not eliminate them. If they are not washed out very well, the next use of the sprayer may kill lots of plants.
You may need three sprayers: one for plant killers, one for broadleaf weed killers and one for other pesticides. I label mine with permanent marker, so the plant killer spray is never used for anything else.
Lawn chemicals intended to kill weeds but not grass can still kill grass when applied incorrectly: in the wrong dosage, at the wrong time of day, during the wrong season or at the wrong time in the grass's life cycle.
Too much of a good thing can be a problem. Never add more chemical than what is recommended in the directions. If the grass is newly planted and has not become established, it is very likely to have problems with weedkillers. Grass under stress from hot weather or drought conditions is more sensitive to herbicides.
Sometimes the grass plant is not entirely killed; the top leaf blades might be chemically burned, but the crown of the plant is still alive. In this case, the plants will recover quickly. Water and fertilize the lawn, and it should respond favorably.
If thin strips of grass or areas smaller than the size of a saucer are dead, it can grow in from the sides. Again, water and fertilizer will help the grass along the edge of the dead areas to fill in the areas. Leave the dead grass in place as protective mulch, and watch for weeds that may sprout.
One of the problem weeds that may sprout is grass that does not match the existing lawn. Watch the color, shape and size of any new grass that sprouts in the dead areas. Weed grass will not look the same and should be pulled when it is noticed. It is often a lighter green color, and the leaf blade is usually much wider than that of lawn grass.
If the dead areas are large, you will have to re-seed or sod the lawn. Matching the type of grass will help the new lawn not look like a patchwork quilt. If you can find out what kind of grass plants were used and buy more of that seed or sod, you will be very lucky. Very few people know what they have in the lawn, let alone their landscaper.
Planting sod to fill in the dead areas is generally difficult due to the size and shape of the dead spots. Digging each spot out so the soil levels of the sod and the existing soil match is difficult. Cutting out sections of the lawn to match the size of the large sod rolls is costly.
If you want to seed the dead areas, get as good of a match to the species and varieties as you can. It is often best to re-seed the entire lawn so the new and old grass varieties will visually blend together.
Jeff Rugg's weekly column, "A Greener View," can be found at creators.com.