Wednesday, April 15, 2009
Weed killer
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.
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Digging around, I found an extensive mat of roots and runners. How can I rout this invasive plant out of my little garden? Is it doomed to be overrun like hers appears to be? I am writing from Massachusetts, and in looking it up online I notice it is listed in the U.S. Agricultural Department as "difficult to eradicate," but that Web site doesn't give instructions about controlling it.
A: You can try to kill out the tops and the roots of Bishop’s Goutweed by applying the herbicide glyphosate to the foliage. If it is already growing close to other plants, use a sponge paint brush to apply the glyphosate solution. Glyphosate becomes inactive in the soil, so you don’t have to worry about it moving underground to kill desirable roots.
Spot treatment will probably not be a one-time activity. Make up a small amount of glyphosate solution each time new treatments are needed. If that doesn't work, you'll have to dig up the weed. Dig and pull carefully when the soil is wet on the day following rain or watering.
Q: I have had trouble growing azaleas on the shaded side of my house in Virginia. The drainage is good there, because my boxwood and liriope do well. I was told that the soil might not have the correct acidity there for azaleas. How can I find out?
A: Take a soil test from the area using a mixture of scattered 4-6 inch deep scoops of soil. Azaleas need an acidic soil with pH of 5.2 to 5.4, while the other plants you mentioned there don’t. Take the samples to your local Extension agricultural agent.
