Look closerPlants
Why poison ivy turns red so early in fall, and what the red is for
When: August to October
Before any maple has started, roadside and stone-wall poison ivy goes brilliant red while its berries turn white. The color is not a warning aimed at us: it is a signal to birds that the fruit is ripe.
Why this time of year
It is one of the first plants to change, turning well before most trees show any autumn color, so late summer into early fall is when a red patch stands alone against everything still green. A vine in full sun on a south-facing wall can color up about a week to ten days ahead of one in shade nearby.
How to notice it
- Scan stone walls, fence lines and tree trunks for a climbing vine with leaves in threes that has gone red while everything around it is green.
- Look for the berries: green through summer, then white or cream. White berries in this region are a strong poison ivy tell.
- Compare a vine in full sun against one in shade a few feet away and see which turned first.
- Learn it now, in color, when it is easiest to see, and you will know it next summer when it is green and hidden.
Try this with kids: Leaves of three, let it be. Can you spot the red one from the car window before a grown-up does?
urushiol is the oil in every part of the plant that causes the rash
Safety
- Look, never touch, and never pick the red leaves. They are as potent as green ones.
- Urushiol is present year round and stays active on fallen leaves, bare winter stems, tools, gloves and pet fur.
- Never burn it. The smoke carries the oil and inhaling it is dangerous.
Sources
- psu.eduPenn State: poison ivy is one of the first plants to change color, turning brilliant red before most plants show autumn color; berries go from green to white; woodpeckers, warblers, vireos and many other birds prefer the berries, so the color reads as a food marker rather than a poison warning; deer, black bears, muskrats and rabbits also eat it.
- mdc.mo.govField guide description including leaves of three, the climbing habit, white fruit, and yellow-to-red fall color beginning in early fall.
- extension.umd.eduExtension identification guidance: leaflets in threes, variable leaf margins, climbing hairy vine, and the year-round presence of urushiol on all plant parts including dormant stems.
In the guide for August, September, October