Why poison ivy leaves change color
Poison ivy is one of the earlier plants to color in fall, and one of the brightest. Here’s why its leaves turn yellow, red-orange, and red, and why they’re still worth keeping your hands off.
The same chemistry as the trees
Poison ivy changes color for the same reasons tree leaves do. All summer, green chlorophyll hides the yellow and orange pigments already in the leaf. As days shorten, the plant breaks the chlorophyll down to reclaim its nutrients, and the yellows and oranges show through.
The reds come from anthocyanins, which the plant makes in fall from sugars trapped in the leaf. Sunlight drives that process, so leaves in full sun along a trail or a field edge usually turn the brightest red, while leaves in the shade often stay yellow. That’s why one vine can show yellow, red-orange, and red at the same time.
An early start
Poison ivy tends to color from early to the middle of the local season, often ahead of the maples above it. It grows where the light is good, along forest edges, fence lines, stone walls, trails, and roadsides, so its red leaves and the red of staghorn sumac are often some of the first fall color people notice.
Still poisonous in fall
The rash comes from urushiol, an oily resin in the leaves, stems, roots, and berries. It doesn’t go away when the leaves change color. Bright fall leaves, leaves on the ground, and bare vines in winter can all still cause a rash, and urushiol can stay on gloves, tools, clothing, and a dog’s fur until it’s washed off.
Never burn poison ivy. The smoke can carry urushiol and cause serious reactions, including in the lungs.
How to spot it in fall
Look for leaves of three, with the middle leaflet on a longer stalk than the two side leaflets. The edges can be smooth or have a few irregular teeth, and the side leaflets often have a notch like a mitten’s thumb. In fall, poison ivy also carries clusters of small, waxy, whitish berries, which birds eat and spread. Older vines climbing trees are covered in fuzzy rootlets that make them look like hairy rope.
Easy to mix up in fall
Virginia creeper turns a similar crimson and climbs the same trees and walls, but it has five leaflets from one point and no hairy rootlets. Poison sumac, a shrub of swamps and bogs, turns brilliant orange and red and carries the same oil. For a side-by-side look at the leaf, see poison ivy in the leaf guide.
Quick answers
Why does poison ivy turn red in fall?
As the leaves wind down in fall, poison ivy breaks down its green chlorophyll and makes red pigments called anthocyanins from sugars in the leaf. Leaves in bright sun usually make the most red.
What color is poison ivy in fall?
Mostly red and red-orange, with some yellow, and often all three on the same plant. Leaves in the shade tend to stay yellow, and leaves in the sun turn red-orange and red.
Is poison ivy still poisonous when the leaves change color?
Yes. Urushiol, the oil that causes the rash, is in the leaves, stems, roots, and berries all year, so colored leaves, fallen leaves, and bare winter vines can all still cause a rash.
Is it safe to burn poison ivy leaves or vines?
No. Smoke from burning poison ivy can carry urushiol and cause serious reactions, including in the lungs.
Keep reading
- Why leaves change colorPigments, timing, and the weather behind a great year
- Why evergreens stay greenAnd the few conifers that do turn
- Why oaks and beeches keep their leavesThe dead leaves that hang on all winter
- Why aspen groves turn at onceWhole hillsides of cloned trees
- Why ginkgo drops its leaves at onceA golden carpet overnight
- What’s happening to ash treesThe emerald ash borer and white ash
Learn to recognize it at a glance.
See poison ivy in the leaf guide