COLUMBUS - Distorted leaves and stems on unrelated garden plants can bear silent witness to two basic truths: By nature, herbicides aren't good for plants. Chemical sprays can drift off-target.

"Plants that are good indicators of accidental weed-killer injury include tomatoes, zinnias, grapevines and redbud trees," said Jake Weber, horticulturist with Kansas State University Research and Extension. "But herbicide drift can cause considerable damage to a variety of yard and garden plants."

The specific symptoms of accidental herbicide injury can vary, he warned. For stems, they often show up as twisting and/or abnormal stretching. For leaves, they can include twisting, cupping, puckering and abnormal stretching. And, the results can range from fewer flowers or vegetables to loss of the plant

Herbicide sprays can drift either as a mist of tiny droplets or as a largely invisible vapor, Weber said. Still, the actual harm they cause will depend on an array of factors:

* Air temperature. The hotter it is, the more vapors gardeners can expect - which is why applying herbicides in the cool of early morning is a good idea.

* Wind, which can help break up a concentration of herbicide particles, but also can carry toxic drift for miles. A calm day is the only safe time to apply chemicals outdoors.

* Amount and duration of non-target plants' exposure.

* Type of herbicide formulation.

* Amount of sprayer pressure. Using a low pressure helps to avoid excessive mist production - which is more likely to drift off-target.

* Stage of plant growth. New shoots and leaves are most vulnerable.

"The most serious plant damage typically occurs early in the season, when plants are actively producing new shoots and leaves. The reason for this is that phenoxyaliphatic acid herbicides - 2,4-D and other weed killers - mainly affect the growing points of plants," Weber said.

Herbicide-damaged plants often need special care to survive summer's stresses, he said. If they can survive, however, they'll probably regain much of their vigor in the next growing season or two.

"To avoid the problem in the future, though, you'll need to remember the factors that can reduce the odds for herbicide drift. And, if you can, you should switch to using a granular formulation of the chemicals you apply in your landscape," Weber advised. "Given the characteristics of drift, your neighbors will thank you for doing that. too."

Herbicide labels provide valuable tips on reducing accidental plant injury, he said. Additional information on how to avoid herbicide damage is available at county Research and Extension offices.