Thursday, August 18, 2005
How to build a better lawn in lousy soil at a new house
John Arbogast
Landscape consultant John Arbogast answers your questions every Thursday. Send questions about your lawn, garden, plants, or insects to:
Dear John
5102 Greenfield St. SW
Roanoke, Va. 24018
Or send an e-mail. Answers will be given only in this column. Please don't send pictures or samples.
Recent columns
Q: I need your advice concerning lawn problems around the 4- year-old house I recently bought on property in the Stonebridge section of Vinton. The lot was a garden for the past 30 years or so but I was told that the contractor stripped the land of the topsoil and hauled it away before starting the house, leaving nasty looking clay that was hastily graded and planted with seed after the construction was complete.
Now the clover, dandelions, Johnson grass and wiregrass are running ramped in the lawn. I got rid of the clover and dandelions with lawn weed killers. However, one corner of the lot is solid Johnson grass, and wiregrass consumes 60 to 70 percent of the rest. It's invading all the plant areas. I have killed it several times, but it comes right back in a few days. I understand that you can't use lawn weed killers in new grass. Any ideas?
A: Take soil tests now from the front and back yards, and work to bring the pH (acidity) to the range needed by turf species in this region 6.5 to 6.8. Also, right now, improve the soil quality with core aerification followed by spreading a thin layer of commercially produced topdressing product or a mixture of finely chopped peat moss and fine soil. “Topdressing” is the turf term meaning to spread a thin layer of soil mix over a turf area to stimulate thatch decomposition and to smooth the surface. Since clay soils become concrete-hard in hot, dry weather and thus become difficult for core aerator penetration, water the lawn two or three days prior to aeration.
To solve the grass invasion problem, chose one of the following remedies:
1. Leave the aggressive wiregrass and Johnson grass, which are both perennials. Your goal in the next years will be to favor bluegrasses or fescues instead of those perennial invaders. In late summer, core aerate the soil and then overseed with 2 ½ pounds of bluegrass mix or 5 pounds of turf-type tall fescue per 1,000 square feet. Fertilize at the time of seeding with any high phosphorus lawn starter fertilizer, and water faithfully every few days as needed to get good establishment. Six weeks after this overseeding, fall fertilize the lawn with a high nitrogen turf-type fertilizer without week killer. Fall fertilizer will help bluegrasses and fescues but won’t benefit the warm season wiregrass. Fall fertilize every future year and don’t apply any nutrients during future springs or summers, as nutrients applied then will benefit wiregrass. Plan to core aerate and overseed every second late summer to keep bluegrasses and fescues predominant and thick so they will hopefully mask wiregrass and Johnson grass there. Accept the fact that wiregrass patches will still be present and will show up as fall and winter brown when cool weather begins.
2. If you can’t beat them, join them. Convert your problem lawn and accept a brown lawn from late fall through mid spring by adding an improved common Bermda grass cultivated variety in late spring or early summer of 2006 to spread along with the existing wiregrass. Take advantage of that summer vigor and heat tolerance of existing wiregrass, which is really wild Bermuda grass. Locate a seed source now becuase improved Bermuda grass is not commonly used in home lawns around here, but don’t overseed your lawn until ‘06. Look for these names: Mirage, Jackpot, Guymon, Sundevil, NuMex Sahara, Sultan, Cheyenne, Sonesta, Primavea. Non-improved common Bermuda grass varieties produce seeds, but they make a very coarse appearing turf. Follow all-parts of the seed establishment routine as described in remedy #1, except use the different time for sowing.
3. This choice provides lawn conversion but also gives a green color year-round along with some required extra work. Do the same as remedy #2, but add the early fall chore each year of core aerating, overseeding, and watering with quick-growing perennial ryegrass.
Q: Will my crape myrtle's roots damage my concrete driveway? It is 20 feet. tall with a 15-inch diameter base. The limbs hang out about 7 feet. My driveway is 5 feet. away. It is probably around 15 years old or older.
A: No, crape myrtle root damage to your adjacent concrete driveway will not likely occur. The roots of this big shrub/small tree grow deeply and are not invasive. This trait is one good reason why crape myrtles have become rather common as a street median beautifier in the upper south.
