🔴 Invasive - Remove
Tree of Heaven
Ailanthus altissima
This is an invasive species that harms native ecosystems. It should be removed when found to protect local plant and wildlife habitats.
Ailanthus altissima
This is an invasive species that harms native ecosystems. It should be removed when found to protect local plant and wildlife habitats.
A fast-growing tree with long compound leaves that smell of burnt peanut butter when crushed, smooth grey bark, and clusters of papery seeds. It is the preferred host of the spotted lanternfly. Seedlings and suckers are pulled, small to mid-size stems come out with a weed wrench, and anything larger is reported for chemical treatment rather than cut.
Native to: China
Brought to Philadelphia in 1784 as a fashionable shade tree and planted along streets for a century because nothing kills it. That is also why it is everywhere now.
Crowds out natives with dense stands, releases chemicals that suppress other plants, and suckers aggressively from its roots — a single cut tree can send up dozens of shoots. It is the spotted lanternfly’s favourite host, so stands seed infestations of that pest into vineyards and orchards.
Colour and texture: Mid-green. Two checks: each leaflet has one or two blunt teeth right at its base, each with a gland underneath. And a crushed leaf or a cut twig smells strongly of burnt peanut butter or rancid nuts.
Leaves: very long (1–3 feet), pinnately compound with 11–25 pointed leaflets. Each leaflet has one or two rounded teeth near its base with a small gland underneath.
Smell: crush a leaf — rancid peanut butter. Native lookalikes do not smell like this.
Bark: smooth and grey on young trees, like cantaloupe skin when older.
Seeds: twisted papery wings in dense clusters, tan to reddish, persisting into winter. Root suckers pop up in a ring around the parent.
Seeds September through the winter.
Dense hanging clusters of flat, papery, slightly twisted seeds, pale green turning orange-tan, staying on the female tree all winter.
Why it matters: One tree can throw hundreds of thousands of seeds, and it is also the preferred host of the spotted lanternfly, so a seeding tree is worth reporting to the coordinator even when it is too big to pull.
Anything with a taproot or shallow roots: garlic mustard, mile-a-minute, seedlings, honeysuckle runners.
Avoid: Do not yank. Speed is what snaps the stem at the root collar and leaves the half that matters behind.
A woody crown too big to pull and too stubborn to cut: wineberry, multiflora rose, barberry, bush honeysuckle, tree seedlings.
It can stay on site. Pulled seedlings can stay, piled off the soil with the roots up.
Staghorn and smooth sumac, black walnut and ash all have long compound leaves. Sumac leaflets are toothed all along the edge; walnut and ash leaves have no glandular teeth at the base and none of them smell of peanut butter. Do the smell test before pulling.
Avoid: Do not clamp halfway up the stem. It snaps, and the crown stays in the ground and re-sprouts.
Before the first cut: Pull seedlings and suckers, wrench anything up to wrist-thick with its root, and never cut a bigger one. A cut tree of heaven answers with a ring of suckers. Note it for the coordinator; big ones get chemical treatment by an approved contractor or the city.
Pull the small ones, wrench the middle ones, report the big ones.