How to Identify Poison Ivy in All 4 Seasons

Are You Sure You Know What It Looks Like?

This poison ivy leaf picture displays the three leaflets for which it is infamous.
Poison ivy leaf with its famous three leaflets. David Beaulieu

 Did you think that you had learned how to identify poison ivy once and for all after you had memorized the rhyme "leaves of three, let it be"? Well, think again! 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 menace -- thereby avoiding getting the rash -- or to hunt down the plant on your property and remove it safely.

But while look-alikes make it difficult to identify poison ivy, they are far from being the sole roadblock. The fact is, Rhus radicans or Toxicodendron radicans (those are the names that botanists have applied to the weed over the years) does not always look the same. Its appearance can change:

  • From season to season
  • As it ages
  • And even from plant to plant

So as you will now understand, learning the "leaflets three" rhyme, while helpful, was just a baby step that you took in discovering how to identify poison ivy. You will have to dig considerably deeper if you wish to rash-proof yourself through your identification skills. That is what I am here to help you with. So pick up the proverbial shovel and let's get digging!

Basic Consideration: Leaf Shape

Besides the fact that poison ivy has a compound leaf (that is, three leaflets or "mini-leaves" joined together), there is very little about its leaf shape that is consistent, except that the leaflets do taper to a point. This lack of uniformity means it is incumbent upon you to expose yourself (safely) to as many of the variations as possible. You can do so by scouring my poison ivy pictures for examples.

Leaflet margins are often smooth, but they can also have tiny "teeth." Sometimes the poison ivy leaf shape includes a notch. In the latter case, a leaflet can have more than one point. Leaf size can vary quite a bit from plant to plant, and they may or may not be glossy.

As you can see from my picture above, the central leaflet is typically joined to the rest of the trio by a comparatively long stalk (that is, much longer than the stalks on the other two leaflets, which are sometimes referred to as the "lateral" leaflets). Notice also that there is a leaf in the picture that is lighter in color than the rest; this is a new leaf that emerged in early summer, against a background of darker, older leaves.

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, really, if you are willing to look at it objectively).
  • Winter: none, because the leaves will have dropped off by this time.

But the leaves do not 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 do not have you convinced or are non-existent, as in winter (note also that this plant can also take the form of either a vine or a shrub.).

For example, in the summer, if you look carefully, you can find poison ivy flowers. I know 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 the berries (called "drupes" if you want to get technical). Poison ivy berries become whitish and waxy in fall (they are a pale green in late summer). Some types of wild birds eat these berries.

This plant is deciduous, so where does that leave you in winter? Is it possible to identify poison ivy during Old Man Winter's reign, or do you have to wait until the leaves reappear in spring?

First of all, poison ivy does not totally disappear during the wintertime: it is a woody plant, maintaining branches above-ground. The question is, How are you going to identify poison ivy branches that have lost their leaves?

Well, you have two identifying traits to work with, potentially:

  1. 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).
  2. It is often 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 what I like to call "hairy vines" (this is why I noted earlier that the plant's appearance changes as it ages). The "hairs" are actually aerial roots. In cases where the poison ivy 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 is necessary at this point to introduce a distinction, namely, that between the plant that we have been discussing so far (Toxicodendron radicans) and a closely-related plant named Toxicodendron rydbergii. What is the difference between the two types? Well, for our purposes, the chief difference, according to the Go Botany website, is that Toxicodendron rydbergii lacks aerial rootlets. So my advice for identifying poison ivy in winter applies only to Toxicodendron radicans.

By the way, you may wonder if it is truly important to know how to identify poison ivy in the winter. The answer is an emphatic, "Yes." Just because its branches are bare, that does not mean it is not toxic. You can receive a rash from poison ivy at any time of year. Unfortunately, if the plant did not produce berries and is not 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!

The best way to grow confident that you can identify poison ivy (and thereby avoid running into it) is to follow the tips I have provided above (and review the pictures that I have linked to) to gain an understanding of what it looks like in all four seasons of the year. When you go on your expeditions, bring a camera and take some photos, so that you can later download them to your computer and compare them to the pictures I have offered. Are you eager to get started? Do you wonder where you can find this weed growing?

Areas in full to partial sun are favored by poison ivy (but do not let your guard down for a moment even in shade, because it can grow there, too), and it is opportunistic about setting up shop where humans have disturbed the soil. You are more likely to encounter it growing at the edge of the forest than in the deep woods. Speaking of edges, it also frequents roadsides. Thanks to those aerial roots, it can be found scaling rock, concrete, brick, etc., as well as trees. This picture of poison ivy climbing a clapboard house wall -- and the damage it inflicted on said wall -- shows the necessity of getting rid of poison ivy if any is growing on your property.