Stamp Out Invasives Now
These very invasive species cannot be killed by spray during the summer months. They grow so rapidly that the week killers knock back only the top of the plants and not the roots.
To kill the roots of perennial plants, the weed killer must translocate downward into the roots and rhizomes. For kudzu, you need only to kill the roots. For bamboo, you must kill both the roots and the rhizomes, the underground stems from which new bamboo canes appear.
Only during the later part of October and early November does the food produced by the foliage of both these invasives translocate down into the roots and rhizomes. The combination of shortened daylight hours, warm days and cool nights sets the stage. In early fall, these plants build up a food supply in their roots so that they can generate strong growth the following spring when soils warm and daylight grows longer.
Spray when foliage on the plants is abundant. Choose a bright sunny day when the soil is moist so that the foliage to be sprayed can absorb the weed killer.
Follow the recommendations provided by the manufacturer for mixing glyphosate (Roundup) with water. To assure greater penetration, add one teaspoon of ammonium sulfate to each gallon of spray to be applied. Wear protective clothing and rubber boots to thoroughly wet the foliage. Use low pressure and a coarse spray to avoid drift. Cover nearby desirable plants with plastic sheeting. Repeat the spray treatment in seven to 10 days.
The kudzu vines will die back to the ground as usual, and if you do a thorough job of spraying, they will not be resuming growth next spring. The bamboo will show signs of dying in about one month following the second application. If you followed the directions, you should not observe any new growth of bamboo next spring, except perhaps at the outer edge of the planting. This can be a problem when there is not adequate bamboo foliage that can be sprayed. If this occurs, allow that bamboo to grow uninterrupted next summer and repeat the treatment that fall.
Ask Dr. Gouin your questions at [email protected]. Please include your name and address.