How Did the Tree of Heaven Get Here? | A Silk Worm’s Failed

You probably know the Tree of Heaven by its smell — a rancid peanut butter aroma that drifts from cracked leaves along highways and vacant lots. The tree itself is hard to miss: fast-growing, thicket-forming, and almost impossible to kill once it settles in.

What you might not know is that its journey from China to North America wasn’t a random hitchhiker story. It was carefully planned. The Tree of Heaven arrived with human ambition, a silkworm fantasy, and a surprising amount of 18th-century paperwork.

The Journey from China to Europe

Before the Tree of Heaven reached American soil, it made a stop in Europe. The first recorded introduction to the West happened in 1747, when a Jesuit priest carried seeds from the Imperial court in Peking to Europe — reportedly on the back of a camel.

A Camel Carries a Tree

That 1747 journey marked the tree’s debut outside Asia. It landed in England and France, where botanists admired its rapid growth and tropical-looking leaves. Within decades, English nurseries began propagating it for export.

Both introductions that eventually reached the U.S. — one in the late 1700s and another in 1820 — came from those same English nurseries. The tree moved west through human trade routes, not by its own seed drift.

Why Early Americans Planted It

America in the 1780s was a country hungry for exotic plants. Wealthy landowners and botanic gardens wanted species that looked impressive and grew fast. The Tree of Heaven fit both criteria. But its appeal went beyond looks — it carried economic promise.

• Ornamental Appeal: The tree’s compound leaves and rapid height made it a popular shade tree in eastern cities. It was planted along streets from New York City to Washington, D.C. throughout the 19th century.
• Silkworm Food Source: The big draw: the tree was thought to be a host for silkworms. If the plan worked, America could produce its own silk without importing from China or Japan.
• Hardiness: It thrived in poor soil, survived pollution, and needed almost no care. That made it ideal for landscaping in growing industrial cities.
• Horticultural Curiosity: Botanic gardens and plant collectors valued it as a rare specimen from a faraway land. It was a status symbol among the horticultural elite.

The silkworm experiment never took off. The worms preferred mulberry leaves, not Tree of Heaven foliage. By the early 1900s, the tree had already started earning a reputation as a weed.

The Silkworm Dream That Fizzled

The timing of the silkworm introduction is key. In the early 1800s, the Ohio DNR notes that the tree was brought for silkworm food alongside imported Asian silkworms. Nurseries heavily marketed it as the “silkworm tree,” and thousands were planted from Pennsylvania to the Carolinas.

But the silkworms refused to eat it. Or at least they wouldn’t produce quality silk on it. The industry collapsed within a few decades. By then, the tree had already escaped gardens and spread into disturbed areas — roadsides, abandoned lots, railroad embankments.

What had been a cultivated exotic turned into an uninvited guest. The tree’s second introduction in 1820, this time as a pure ornamental in New York, only added to the population. Nobody was cutting them down yet.

What Made It Take Over

The Tree of Heaven didn’t just survive in America — it thrived. A few biological advantages turned a planned import into an invasive nightmare.

1. Allelopathic Chemicals: The tree releases compounds into the soil that stunt or kill competing plants. This chemical warfare clears the ground around it, leaving room for its own seedlings.
2. Rapid Growth: It can grow 6 to 10 feet per year in good conditions. That speed lets it outgrow native trees and shrubs in disturbed sites.
3. Tolerance for Poor Soil: It grows in compacted clay, acidic ground, and even cracks in pavement. Urban lots are its natural habitat.
4. Massive Seed Production: A single mature tree can produce 300,000 seeds per year. Wind and water carry them far from the parent.

By the 21st century, the Tree of Heaven was classified as a noxious weed in multiple states and considered one of the worst invasive species in Europe and North America. What started as a horticultural experiment now costs millions in control efforts annually.

Where It Spread After Introduction

The tree’s range expanded in two waves. First came the ornamental plantings in eastern cities — Philadelphia, New York, Washington. Then, after the silkworm failure, seeds spread naturally along rail lines and road corridors.

The University of Arkansas Extension’s guide on tree history references the first introduction in 1747 as the starting point for its global journey. From that single camel ride, the tree reached nearly every continental U.S. state by the 1900s.

Forest surveys suggest that while the tree arrived in Pennsylvania around 1784, it didn’t become a widespread problem until the mid-20th century. Disturbance from urbanization and road construction gave it the open ground it needed to explode.

The Bottom Line

The Tree of Heaven arrived in America through deliberate human choice — first as a beautiful ornamental, then as a failed economic crop. Its spread from those original plantings into nearly every continental state happened because it’s biologically equipped to dominate disturbed soil. Two centuries later, removing it is far harder than planting it ever was.

If you’re dealing with this tree on your property, your local cooperative extension service or a certified arborist can recommend control methods — cutting alone often makes it spread faster, so timing and technique matter for your specific situation.