Editor’s note: Kelly R. Jackson takes questions called into his phone recently at the Christian County Extension Office and answers them in the Garden Corner column.
Question. How do I keep bermudagrass out of my tall fescue lawn?
Answer. Bermudagrass in a difficult weed to control in tall fescue lawns. It has tolerances to heat, drought and traffic stress giving it the advantage. Also Bermudagrass spreads by underground lateral stems (rhizomes), above ground lateral stems (stolons), and to a lesser extent, by seed making it quite aggressive and invasive. Since it is a warm season grass, Bermuda turns brown with the first hard frost leaving behind ugly blotches in your green lawn. Although it is tough, with some intensive management it is possible to restrict its spread (suppression) and even remove Bermudagrass from lawns (control). The following management plan was developed by the University of Tennessee for tall fescue lawns:
n Apply the herbicide Fusilade II at 6 fluid ounces per acre or Acclaim Extra at 28 fluid ounces per acre plus Turflon Ester at 1 quart per acre beginning mid-May. Apply sequential applications every 4 weeks throughout the growing season ending Aug. 15.
n Reseed tall fescue into the controlled or killed areas.
n Increase mowing height to greater than 3 inches.
n Fertilize Sept. 15, Nov. 1, and March 1 with 1 pound of nitrogen per 1,000 square foot to encourage vigorous tall fescue growth. Do not fertilize tall fescue after April 1 or before September 1.
Even though there may not be a quick fix to Bermudagrass troubles, with patience and persistence you will be able to return your lawn to the Bermuda-free zone you’re seeking. As always, before using any chemical, read and follow the directions carefully.
Q. Is it safe to build raised beds out of pressure treated lumber?
A. The primary concern of using pressure treated wood to construct raised beds is in regards to the products used to treat the wood.
For many years, lumber was treated with arsenic found in CCA (chromated copper arsenate). Research from Pennsylvania State found that the chemical does leach out of the wood into the soil and is taken up by the plants in small amounts. However, the level of chemical is not significant enough to be of concern for human health. In addition, the EPA restricted the sale of CCA treated lumber in 2004 and today it is more likely treated with ACQ, an alternative wood-treatment chemical that contains no arsenic, chromium or any other chemical considered toxic by the EPA.
It does contain copper, which plants and our bodies need in small amounts, and the copper can leach into the soil; but a published study in 2007 showed that the exposure to copper from ACQ treated wood is not expected to have adverse effects on the health of adults or children. CA (copper azole) is another wood preservative utilizing copper; its risk should be similar to ACQ. Creosote, a product used to treat railroad ties, may cause injury or death to plants while it is still fresh on the ties. But old discarded ties will not injure plants. Still concerned? Consider lining your raised bed with a heavy-grade plastic to separate it wood from the soil.
You can also leave 10 to 12 inches of space between the sides of the beds and your plants as an extra precaution. Finally, when harvesting root vegetables, wash off all the soil to reduce exposure.
Kelly R. Jackson is the Christian County Extension Agent for horticulture. He can be reached at 270-886-6328 or visit Christian County Horticulture online at www.christiancountyextension.com.