Down the Garden Path: How well do you know poison ivy?

Experienced gardeners know where poison ivy is likely to be found in the home landscape and what it looks like in its various forms and stages of growth. That may not be the case for newer gardeners or those having moved from an area relatively free from poison ivy to a wooded area or neighborhood. Without knowing it is in the yard, it is all too easy to get the oils on your hands and clothing while clearing beds of otherwise harmless weeds.

Until you can easily identify poison ivy, the adage “leaves of three, let it be,” is pretty good to live by. Mature poison ivy provides birds the berries that later become seeds deposited along fence rows, beneath deciduous and evergreen tree canopies and shrub borders.

Poison ivy seedlings

As a small seedling, poison ivy is not easily recognizable and may look like many other immature weeds. This is one of the forms and stages where poison ivy is found, a typical weed in the garden. As seedlings grow, the characteristic leaf trios begin to develop.

Poison ivy vines

As the seedling continues to grow, it moves to a vining growth habit for its next form, with the leaves clearly looking like all the pictures we see. As a vine, it easily can hide in a bed of ground covers, reaching out into the lawn from the edge of the woods or climbing the house wall with Boston ivy or other ornamental vines. Gardeners also will find it while pruning their shrubs.

Poison ivy with aerial roots

When the poison ivy vine runs into a tree trunk, the third form shows up as a vine that can cling to the bark using brown aerial roots. This form, as a vine climbing the tree, becomes the mature stage, where, well up in the tree canopy, it has very large leaves, again with the typical three leaflets. But those leaves may be 2 feet in size. Besides the gigantic leaves, this is where the vine begins to flower and fruit annually. Poison ivy has outstanding reds and oranges for fall color and is quite attractive. Just remember: Look, but don’t touch.

Poison ivy control

In the home landscape, removing poison ivy while it is small and before it begins to vine is best. It is the oil in the plant that gives us the dermatitis; watery blisters are common. Young seedlings will die if pulled out and left to dry. Handle them as little as possible. You can use a digger of your choice so you do not come in contact with the plants. Wearing an unlined rubber glove is a good idea, too. With plants slightly bigger, gardeners could use a glyphosate product, but use it very carefully around valuable ornamentals. And always read and follow label instructions and safety measures.

If you find yourself with one of those vines up a tree, carefully cutting through the vine at the soil line is the best option. Do not remove the vine. Leave it there to dry in the tree. No need to pull it down. Treat that vine stump, too. Vines growing up the tree can be as small as a quarter of an inch to more than 3 inches in diameter for a larger mature vine.

Not just a summer issue

All parts of poison ivy can give you dermatitis, and you can get a reaction even in the winter when plants and vines are dormant. Never burn poison ivy, as the oils will be in the smoke.

• Richard Hentschel is a Horticulture Extension educator with University of Illinois Extension, serving DuPage, Kane and Kendall counties. This column originates on his blog at To get more tips from Hentschel, watch his “This Week in the Garden” videos on Facebook and YouTube.