By Mark Czarnota
and Tim
Murphy
University of Georgia
Everyone who works outdoors with plants or goes hiking, camping,
picnicking or other outdoor activities should be able to identify
poison ivy. Failing to know it when you see it can lead to severe
allergic reactions.
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Poison ivy (Rhus radicans) is found mostly in moist,
deciduous forests and wooded areas. Unfortunately, it’s also
found on trees, fences and ornamental plantings in Georgia
landscapes.
A related species, poison oak (Rhus toxicodendron), may
actually be a type of poison ivy.
Poison ivy may grow as a small shrub or a high-climbing vine on
trees, fences and buildings. Each compound leaf has three bright
green, shiny leaflets.
Remember the rule
The shape of the leaves and presence of hairs on the undersides
vary greatly, so people may not always recognize poison ivy. The
old saying, “leaflets three, let it be,” is a good rule.
Poison ivy has small flowers with five yellowish-green petals
arranged on slender stalks. Its small, grayish white berries are
food for more than 55 bird species.
Box elder (Acer negundo) is often confused with poison
ivy. Its seedlings have three leaflets, too, but they have
opposite leaves. Poison ivy leaves are alternately arranged on
the stem. Virginia creeper (Parthenocissus quinquefolia)
can look like poison ivy, too. But its leaves usually have five
leaflets.
The Rhus cousins are said to cause more contact dermatitis
(redness, rash, blisters and itching) in the United States than
all other plants and industrial or household chemicals.
All poison
All parts of poison ivy are poisonous year-round. A toxic, oily
compound (urushiol) is quickly exuded if plant tissues are broken
in any way. People are exposed as they brush against the plant or
touch equipment, clothes or pets that have touched it. It can
even be carried in the smoke from burning the vines.
Only the oily toxin, though, can spread the rash. Symptoms
usually appear in 12 to 48 hours but may not show up for days.
If you think you’ve contacted poison ivy, washing your skin with
cold water within 5 minutes may keep the urushiol from contacting
your skin. Within the first 30 minutes, use soap and water.
Consult a physician or pharmacist for the best treatment.
Continually clipping poison ivy at or near the ground will
eventually control it. But you may have to clip it several times
during the year for several years.
Can you dig it?
Digging poison ivy plants and roots can control it in small beds
of landscape ornamentals. Be sure to wear watertight gloves,
though.
Herbicides can control poison ivy, too. But always read all label
directions. Poison ivy has extensive roots, so you’ll likely have
to apply herbicides many times.
Glyphosate is the active ingredient in Roundup and many other
products. Apply it directly to the foliage of poison ivy. It
works well on warm, sunny days when plants are actively growing.
It’s best when plants are flowering or fruiting, generally in
early summer in Georgia.
You’ll need at least one rain-free hour after applying glyphosate
to get the best results. The product can severely injure
desirable plants, so don’t spray it on windy days. Use coarse
sprays with large droplets to minimize drift.
Cut and spray
Where poison ivy has grown into large trees, cut the vine 2 to 3
feet above the soil. Within 24 hours, spray the leaves of the
lower section (if any) with a 5-percent to 10-percent glyphosate
solution (using at least a 41-percent glyphosate concentrate to
make the spray solution).
If there are no leaves, paint or spray the lower stem portion
with 50-50 glyphosate-water solution or undiluted glyphosate
(with at least a 41-percent glyphosate concentrate.
Triclopyr (Brush-B-Gon) is recommended around homes, fences and
nongarden areas.
It’s often used to keep poison ivy and other plants from coming
back after being cut. Just clip the poison ivy vine near the soil
surface. Then paint the freshly cut surface with undiluted
triclopyr. Don’t apply it, however, to the bark of any trees.
Repeat the treatment when regrowth appears.
(Mark Czarnota is a Cooperative Extension horticulturist and
Tim Murphy an Cooperative Extension weed scientist with the
University of Georgia College of Agricultural and Environmental
Sciences.)
