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PLANTS : Poison Ivy Has Several Vine Points

November 18, 1995|From Associated Press

One of the best vines for autumn color is decked out in its fall finery. Actually, the leaves have been quite attractive throughout the season, beginning in spring, when, glossy and tinged red, they foreshadowed their glossy green of summer and their fiery crimson of fall.

The vine is poison ivy ( Toxicodendron radicans ).

Except for one shortcoming, poison ivy is a vine of many virtues. Here is a plant immune to pests, a plant that can take the form of a mounded shrub or, given support, quickly clothe a tree trunk or post.

No doubt the fall color casually attributed to trees in the forest (perhaps viewed from a swiftly moving car) often owes its splendor to poison ivy vines exuberantly climbing and living among the branches.

If the plant were more benign, you might even appreciate the interesting quality of the aged stems, which look like thick, hairy arms pulling the plant up tree trunks. Viewed objectively, the white berries enhance poison ivy's beauty, but appreciation for the berries is tempered by the realization of how effectively they disperse the plant as they are eaten by birds.

It is a pity that poison ivy has that one shortcoming, the nasty rash it inflicts on people.

At least half of us reputedly are susceptible, a condition we acquire in childhood but which decreases as we age. The culprit is an oily chemical called urushiol. It is just waiting to be released from resin ducts in the leaves, flowers, fruits, roots and bark, or even as droplets into the air when the plant is burned.

Poison ivy's virtues show that at least it does come from a good family ( Anacardiaceae ). The members include notable ornamentals such as sumac, including the low-growing, fragrant sumac and the almost tree-like wild and cultivated forms of staghorn sumac.

Poison ivy's kin also includes some delectable edibles, such as mango, cashew nut and pistachio nut. The chair on which you are sitting may have been coated with a preparation made from the sap of another relative of poison ivy, the lacquer tree.

Not all the genteel members of the family have kept aloof of poison ivy's shortcomings. Mango skin causes a rash in some people, and all cashew nuts are heated slightly after they are harvested in order to drive off their volatile, irritating oil. Some people get a reaction when they touch lacquered furniture.

Getting rid of poison-ivy plants is no easy task because of their uncanny capacity to keep re-sprouting each time their tops are lopped off.

But diligence pays. No plant, not even poison ivy, can live without food, and the plant eventually does die if the tops are repeatedly removed with gloved hands (be careful when you touch the gloves), chewed off by goats (goats are immune to poison ivy) or shaded with a thick or impenetrable mulch.

Midsummer is the best time to attack the plant, because severing the top from the roots now is, from the plant's viewpoint, nothing more than an early winter.

Herbicides also are effective against poison ivy but must be used with caution to ensure that no other plants or animals are harmed. Read the label carefully to make sure the particular herbicide is specifically effective against poison ivy, and then follow directions to the letter.

It is not feasible to permanently eradicate poison ivy. The best approach is to learn to recognize it ("Leaves of three, quickly flee; berries white, poisonous sight!"), to live with it, to appreciate its color from a distance and to kill it when it creeps too close.

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