Herbicides can rid gardens of unwanted poison ivy

Tulsa World
by: Staff Reports
5/31/2008 12:00 AM

ASK A MASTER GARDENER

The Master Gardener: Vija Sevier

Q. I have poison ivy in my yard, under a cedar tree. I am very allergic and get a rash if I just get close to the vine. What should I do to get rid of it? Ruth Ann W. Sand Springs

A. Poison ivy can definitely take the fun out of gardening or a summer picnic. It is very common in Oklahoma and is one of the big three plants in the United States that can produce a severe contact rash. It is estimated that more than three-quarters of the population is allergic to poison ivy. The other two plants are poison oak and poison sumac, but these two plants are rare in our area.

Poison ivy is distinctive in its leaf, which is a cluster of three pointed leaflets, which can have either smooth or toothed edges. The leaves vary in size from 1 to 5 inches in length and the stem on the middle leaflet is longer than the others. It may be a low-growing vine, a shrub or a large tree-climbing vine, easily identified by a thick covering of root hairs. These vines may be several inches thick and climb many feet into trees. These are the pretty red vines in trees one sees along the highway in early fall.

Although poisonous to humans, poison ivy's grayish-white berries are eaten by birds with no harmful effects. These characteristics have produced two well-know rhymes for avoiding the plant:

"Leaves of three, let it be; berries white, danger in sight."

"Leaves of three, let it be; hairy vine, no friend of mine."

The poison is an oil - urushiol - and is found in all parts of the plant - leaves, stems and roots. It is easily absorbed by casual contact. The toxin is easily absorbed onto clothing where it may persist for months if not washed. It also may be spread by pet fur and in droplets in smoke, if the plant is burned.

Urushiol can be washed from the skin with soap and water if done soon after contact. For a more complete removal of urushiol, physicians from the FDA recommend washing exposed areas of skin with isopropyl (rubbing) alcohol, before using soap and water. Once absorbed by the skin, it cannot be washed off. A rash develops hours to days after contact in sensitive people. Once developed, the skin rash will not spread the toxin to other people, which is a common misconception.

Poison ivy may be eliminated by digging and removing plants - roots and all - or with herbicides. It is not a good idea to use a weed-eater, for obvious reasons. Any planned contact with the plant should include disposable rubber gloves, long sleeves and eye protection. Immediate washing of clothing with standard laundry detergent will remove any toxin. All plant parts should be bagged and discarded.

Herbicides are effective but may need more than one application. Glyphosate, found in Roundup, or triclopyr, which is found in Bayer Brush Killer Plus or Ortho Brush-B-Gon Poison Ivy, are the chemicals recommended. The labels should be followed carefully, because each herbicide has different characteristics.

Triclopyr is the more effective, will not kill grass in the area, but persists in the soil for several weeks and replanting cannot be done during that time. Glyphosate does kill grass and any green growing plant it comes in contact with but is inactivated by the soil and has no significant residual activity. Both glyphosate and triclopyr are most effective when applied to poison ivy when it is rapidly growing.

Glyphosate concentrate can be used to paint the stumps of vines immediately after they have been cut; this is very effective in killing any vine. It is especially effective on the large poison ivy vines attached to tree trunks.

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