Tree of Heaven
Ailanthus altissima · Simaroubaceae · Deciduous · also called ailanthus, stink tree
Tree of heaven is one of North America's most aggressive invasive trees and the preferred host of the spotted lanternfly, which makes correct identification a matter of some public interest. Crushed leaves smell strongly of rancid peanut butter, which is the fastest confirmation there is.
Quick facts
- Arrangement
- alternate
- Leaf
- Very long compound leaves with 11 to 41 leaflets, each smooth-edged except for one or two blunt teeth near the base with a gland underneath.
- Bark
- Smooth pale grey with faint lighter vertical streaks, often likened to cantaloupe skin.
- Fruit
- Large clusters of twisted single-winged samaras, often persisting bright orange-red into winter.
- Height
- 40–80 ft
How to confirm it
- Crush a leaflet: a strong unpleasant smell, often described as rancid peanut butter or burnt rubber.
- One or two blunt teeth near the leaflet base, with the rest of the edge smooth. Sumac and walnut are toothed along their whole length.
- Smooth pale bark with lighter streaks.
- Suckers aggressively from roots, forming thickets.
What it is confused with
One observation settles each of these.
Sumac leaflets are toothed the whole way along and the twigs are densely velvety. Sumac fruit is an upright red cone.
Walnut leaflets are toothed throughout and the fruit is a green ball, not a winged samara.
Where it grows
Across North America, in disturbed ground, along railways, in alleys and any neglected corner.
Start here: opposite or alternate?
Look at where the leaves join the twig. Are they in matched pairs directly across from each other, or staggered one after another? The vast majority of trees are alternate, so finding an opposite tree removes almost everything else in one step.
In North America, opposite-leaved trees are remembered as MAD Cap Horse: Maple, Ash, Dogwood, Caprifoliaceae (viburnums and elders), and Horse chestnut. That is very nearly the whole list.
Check partway along a healthy twig rather than at the tip, where crowding can make alternate leaves look paired. And check more than one twig.