The Problem

Tree of Heaven isn't just another fast-growing tree. It actively poisons its competition, colonizes ground nothing else can, and spreads in ways that make half-measures backfire.

Where it came from

Ailanthus altissima is native to China, where it was traditionally used in medicine and as a host for silkworms. It was introduced to North America as an ornamental and street tree in the late 1700s and 1800s, prized for tolerating poor soil, pollution, and neglect — the same traits that now make it so hard to stop.

It poisons the competition

Tree of Heaven produces a toxin called ailanthone in its roots, bark, and leaves. Released into the soil, it suppresses germination and growth in nearby plants — an effect called allelopathy. It's not just outgrowing native seedlings around it; it's actively working against them.

It grows fast and colonizes anything

Established trees can grow up to 6 feet a year and reach 90 feet tall. That speed lets it overtop and shade out slower native competitors before they get established. It also aggressively colonizes disturbed ground — vacant lots, roadsides, even cracks in pavement and foundations — sites most other trees can't touch.

It damages infrastructure

Its aggressive root system cracks sidewalks, foundations, and sewer lines, which is a real part of why municipalities spend money removing it — this isn't only an ecological problem.

How it spreads

Two mechanisms, and the second one is the reason removal has to be done right:

• Seed. A single mature female tree can produce 300,000–350,000 wind-dispersed seeds a year.
• Root suckering. It also spreads vegetatively from its root system, and from cut stems left on the ground. Critically, cutting or mowing a tree down without treating it chemically stimulates aggressive root suckering — you can end up with a denser thicket than you started with. This is the single most important thing to know before you touch one. See How to Remove It for what actually works.

A forward-looking concern: spotted lanternfly

Tree of Heaven is the preferred host plant of the spotted lanternfly (Lycorma delicatula), an invasive planthopper that has caused serious agricultural damage since establishing in Pennsylvania in 2014. Spotted lanternfly is not currently established in Washington or the Pacific Northwest — only isolated interceptions have been reported in neighboring states. But climate modeling suggests the Pacific coast is suitable habitat long-term, and removing its favorite host here is a real prevention measure, not a reaction to an active local infestation.

Regulatory status in Washington