Thursday, July 19, 2007
Use synergy to kill white clover
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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Q: What product and when is the best time to kill white clover? I live in the Adirondacks.
A: I’m assuming that your question pertains to white clover elimination in a lawn of bluegrass, tall fescue and/or perennial ryegrass.
White clover is a perennial plant. It may take two or three years to kill it. Clover leaves need to fully absorb the herbicide you're using to kill them, so weed and feed formulations typically won't give you the results you're looking for. The dry granules of such products will likely fall to the ground, rather than absorb into the clover leaves.
I'm sorry that I can’t tell you the shelf name of the product you should use. Synergism is your best bet in controlling difficult lawn weeds like white clover. With synergism, two or more products work together to increase the effect of each one alone. A lawn weed killer to control white clover should contain the following ingredients:
- Dicamba; 2,4-D + Mecoprop
- 2,4-D + Mecoprop + Dicamba
- 2,4-D + Dicamba
- 2,4-D + Dichlorprop + Mecoprop
- 2,4-D + Triclopyr or
- Triclopyr + Clopyralid
Here in Virginia, October and November seem to be the most effective times to begin your white clover control. That’s when new white clover plants are young, tender, and most easily killed. Up in the Adirondacks, that tender time is probably two to four weeks earlier in the fall. Ask a local lawn and weed expert for advice on timing.
Add another thing to your white clover control effort. White clover is a legume, meaning that it naturally removes the nutrient nitrogen from the air and “fixes” it so this nutrient will be available in the soil. The presence of lush white clover can indicate that the lawn soil needs more nitrogen and that white clover will be present there to help out until the lawn is getting enough nitrogen from fertilization.
Q: What would you recommend doing to prevent my neighbor's bamboo plants from invading my flower beds? It is planted alongside our privacy fence and preventing it from encroaching on our yard creates an ongoing challenge for me.
A: Hopefully, you have enough space along your privacy fence to fit some digging equipment. Invasive bamboo can be stopped by constructing a physical deterrent and then watching the area during the growing season to eliminate any bamboo shoots that manage to come around or underneath the deterrent. This is especially important if the deterrent could not be constructed deep enough or continuously all along the border.
Rent a Ditch Witch or similar type of deep-trench digger and dig a narrow trench at least 33 inches deep on your side of the privacy fence. The barrier should extend at least 15 feet beyond each end of your neighbor’s bamboo plants.
Insert a barrier that won’t rot or decay in the trench you've dug. I’d use aluminum panels made for metal roofing or maybe fiberglass sheets, which are available at some home stores. You could just fill the trench with concrete, but the amount of concrete needed could be rather expensive.
To conduct your “search and destroy” mission for new bamboo shoots on your side of the fence, walk over the potential bamboo zone wearing old work boots and kick over any new shoots spotted. If you discover any shoots taller than 18 inches, kill them with a ready-to-use spray bottle of Roundup. Be careful with your aim, so that the chemical doesn’t accidentally land on green parts of your lawn or flowerbed plants.
Q: What is the yellow fungus on one of my clematis vines -- and what do you recommend that I do to stop it?
A: Clematis vines can be infected with a “rust” disease, so named because of the color of the little pustules created by the rust fungi as part of their reproduction. This rust powder is orange, I believe, rather than the yellow that you mentioned. I don’t know of a curative product for rust disease on clematis parts, but I don’t believe that this rust infection is serious.
I do know of a yellow-colored fungal fruiting structure that can grow on constantly damp wood or bark surfaces. These yellow things are not destructive themselves, so physical removal of the growth is all that you can do. However, you should examine your clematis and its surroundings to find what has allowed the surfaces of the plant to become damp continuously so that the fungal fruiting body has grown. Frequent overhead watering during the evening can cause this type of fungal fruiting body, because it allows the clematis parts to stay damp for a long time. If you water at night, change your watering schedule to the early to mid-morning hours so that plant surface will have time to dry before dark. Also, reduce the frequency of your plant-watering.
