Friday, August 22, 2008

Landscape - Woody Vining Weed Control

Woody vining weeds can be difficult to control in the landscape. The following are some recommendations.

Woody-vine control in landscape plantings

No selective herbicides exist that allow you to chemically control woody vines growing among broadleaf ornamentals. Cultural controls include hand weeding and repeated cultivation. Cutting the stems at the soil line does not control these weeds due to re-growth from rootstocks. Cutting the vine at the soil line and then treating the young re-growth with a systemic herbicide is an option when you cannot easily spray the weed's foliage without contacting foliage of desirable plants.

Spraying a contact herbicide such as diquat or pelargonic acid will affect the foliage but will not eliminate underground portions of the vine. (Repeated application gradually can deplete the root reserves of a perennial if you continually spray the re-growth.) A physical barrier such as black plastic or a landscape fabric suppresses establishment of these weeds from seed. However, mulches are ineffective for controlling perennial vines that already are established. Therefore, chemical control is limited to non-selective post-emergence herbicides such as glyphosate (Monsanto's Roundup Pro) and glufosinate ammonium (AgrEvo's Finale).

Roundup Pro, a systemic herbicide, is the compound of choice for most situations because it translocates to roots of perennial vines. However, you may need to make repeated applications to completely kill a perennial vine with a deep, well-established root system. Finale is a contact herbicide with limite translocation in plants. You can expect regrowth from the rootstock following an application with this product, and you'll probably need repeat treatments for long-term control.

To avoid injury to nearby ornamentals when you spray with Roundup or Finale, use a shielded spray. When using directed sprays, avoid contacting the bark of young trees or species with thin or green bark. Both Roundup and Finale can cause bark injury to such plants. Wiper applications of Roundup are another way to apply this herbicide near sensitive ornamentals. You'll need to use higher concentrations of Roundup with wipers-check the label for specific use directions.

You can apply Finale anytime weeds are actively growing. In general, the optimum time to apply Roundup is in late summer to early fall (this range of times is greater in warmer climates), but before frost. One exception is greenbrier, where spring applications are necessary because its older leaves apparently do not readily absorb the chemical. You also can apply Roundup to cut stems or stumps, or inject it into stems, for controlling individual plants. You should make such treatments to actively growing vines immediately after cutting the stem.

Information from Jeffrey Derr, Associate Professor of Weed Scienc, Virginia Polytechnic Institute and State University.

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