Don't think that you've learned how to identify poison ivy once and for all after you've memorized the rhyme "leaves of three, let it be!" There are plenty of look-alikes that bear foliage comprised of three leaflets. You must take your identification efforts to the next level if you wish to venture out into the brush with the confidence that you can sidestep this perennial menace (thereby avoiding getting the rash) or hunt down the plant on your property and remove it safely.
But while look-alikes make it difficult to identify poison ivy, they're far from being the sole roadblock. Rhus radicans (alternately called Toxicodendron radicans), itself doesn't always look the same. Its appearance can change:
- From season to season
- As it ages
- And even from plant to plant
So, as you'll now understand, learning the "leaflets three" rhyme, while helpful, was just a baby step that you took in discovering how to identify poison ivy. Just to begin with, be aware that this plant can take the form of a shrub, of a climbing vine, or of a creeping vine. So you'll have to dig considerably deeper if you wish to rash-proof yourself through your identification skills.
Basic Consideration: Leaf Shape
Besides the fact that poison ivy has a compound leaf (three leaflets or "mini-leaves" joined together), there's very little about its leaf shape that's consistent, except that the leaflets do taper to a point. This lack of uniformity means it's incumbent upon you to expose yourself (safely) to as many of the variations as possible.
Leaflet margins are often smooth and even, but they can also have tiny "teeth" and/or be wavy. Sometimes the poison ivy leaf shape includes a notch. Leaf size can vary quite a bit from plant to plant, and the top surface of the leaves may be glossy or dull.
The central leaflet is sometimes bigger than the other two. It's typically joined to the rest of the trio by a comparatively long stalk (much longer than the stalks on the other two leaflets, which are sometimes referred to as the "lateral" leaflets).
One leaf on a plant may be lighter in color than the rest; this is often a new leaf that emerged in early summer, against a background of darker, older leaves. The bottom part of the leaf often is covered in tiny hairs, usually has a lighter color, and is always dull.
Tips to Help You Identify Poison Ivy in Each Season
The most obvious way in which poison ivy's appearance changes from season to season is in leaf color:
- Spring: various shades of red or orange
- Summer: green
- Fall: red, orange, or yellow (quite spectacular in some cases, as is also true of poison sumac)
- Winter: none, because the leaves will have dropped off by this time
But the leaves don't tell the whole story. You can apply the knowledge you gain here about other plant parts to help you identify poison ivy when the leaves, alone don't have you convinced or are non-existent, as in winter.
For example, in the summer, if you look carefully, you can find poison ivy flowers. That may sound odd to beginners: The word "flowers" evokes images of beauty, and few would deem this plant beautiful in the summer. But poison ivy does bear clusters of small, greenish-white flowers.
Likewise, autumn brings with it another way to identify poison ivy: by its berries (called "drupes," technically). The berries become whitish and waxy in fall (they're pale green in late summer). Some types of wild birds eat these berries.
Identifying Poison Ivy in Winter
Poison ivy is deciduous. This means you won't be able to identify it by its leaves in winter. Luckily, there are still ways to identify the plant even when it's leafless.
Poison ivy doesn't totally disappear during the wintertime: It's a woody plant, maintaining branches above-ground. You have two ways, potentially, to identify such branches as poison ivy branches:
- If the plant produced berries during the past summer and fall, some of those should still be around in winter (although their appearance will be somewhat weathered).
- It's easy to identify poison ivy plants that are older (at any time of year) via their aerial roots.
Regarding this second identifying trait, plants that have been around for a while can grow quite large, becoming "hairy vines." The "hairs" are actually aerial roots. Thanks to these aerial roots, poison ivy can be found scaling stone walls, rock faces, concrete, brick, etc., as well as trees. It can climb up a clapboard house wall and do damage to the wall, a fact that further shows the necessity of getting rid of poison ivy if any is growing on your property.
In cases where the vines are clinging to a tree, at first glance you may think that these little fibers are part of the tree, itself. But a closer look will reveal that the vine has embedded itself tightly into the tree.
Note: It's necessary at this point to introduce a distinction between the plant that we have been discussing so far (Toxicodendron radicans) and a closely-related plant named Toxicodendron rydbergii. The difference between the two types, for our purposes, is that Toxicodendron rydbergii lacks aerial rootlets. So identifying poison ivy in winter can be easier when it comes to Toxicodendron radicans, specifically.
It's important to know how to identify poison ivy in the winter despite the fact that all its leaves will be gone. Just because its branches are bare, that doesn't mean the plant's toxic oil, urushiol, won't still cause a rash. You can get a rash from poison ivy at any time of year, and you can also get a rash from the dead plants. In fact, if another object becomes tainted with urushiol and you touch that object, you can come down with the rash. So it's quite possible to become a rash victim even if you've been careful to avoid coming into direct contact with this weed.
Unfortunately, if the plant in question didn't produce berries and isn't old enough to have acquired that hairy look, you may have to wait until spring to get a positive ID on it. So be careful in the meantime while you wait out the winter!
Where Poison Ivy Grows, Tips for Studying It
There are apps you can download onto your phone to identify poison ivy and other wild plants. But these apps don't do you much good if your footstep is about to take you into a thicket of questionable weeds and you have to make a snap decision as to whether or not to change direction to avoid a possible rash. The only way to grow truly confident that you can identify poison ivy is to build on the basic knowledge you have gained here.
You must put in the work, yourself and become intimately familiar with what it looks like in all four seasons of the year. By making its identification a personal project, you'll reinforce your knowledge at an instinctual level. Avoiding poison ivy will become second nature for you.
The best way to do this is to take pictures of poison ivy on your phone. Whenever you go out into the woods and encounter poison ivy in a different form (with berries, with its fall color, etc.), snap a picture of it and add it to your gallery of poison ivy pictures so that you can refresh your memory at your own convenience.
To undertake such a project, begin by understanding where you can find this weed growing. Areas in full to partial sun are favored by poison ivy (but don't let your guard down for a moment even in shade, because it can grow there, too), and it's opportunistic about setting up shop where humans have disturbed the soil. You're more likely to encounter it growing at the edge of the forest than in the deep woods, and it also frequents roadsides.