The Tree of Heaven (Ailanthus altissima) got its name from the Indonesian word “ailanto” or “ailanthus,” meaning “tree of the gods.” A better name for the tree would be Tree from Hell because it outcompetes other plants wherever it grows. Arborists considered it a “trash tree” because it is too good at surviving in all the wrong ways. Homeowners and their neighbors with mature Ailanthus trees get tired of pulling up sprouts, picking up branches, and racking up copious amounts of debris throughout the growing season. If left alone, Ailanthus saplings grow into full-sized trees quickly. The tree is so unpopular that a group of Denver residents has created a website, Denver Tree of Heaven, dedicated to its eradication.
The Tree of Heaven was introduced to Philadelphia by a Pennsylvanian named William Hamilton, who brought it from China and planted it at his estate, The Woodlands. Hamilton, a very successful Philadelphia lawyer, bought the estate in 1735. He was an active botanist and introduced Ginkgo, Sycamore maple, and, unfortunately, the Ailanthus to America. The estate still exists and is now a National Historic Landmark. Hamilton was fascinated by fast-growing and unusual plants from Asia, so Ailanthus’s lush foliage and rapid growth caught his eye. American cities planted Ailanthus because it provided fast shade, tolerated poor soils, and remained lush in crowded cities as our country grew. By the turn of the last century, the tree’s foul smell, invasive roots, and aggressive growth earned it a far less flattering nickname: the “Tree from Hell.”
What Makes The Tree of Heaven A Trash Tree?
The Ailanthus, at first glance, is an attractive tree; however, it is an aggressive species for the following reasons.
- Grows Like A Weed
The tree grows incredibly fast, outcompeting native species for sunlight, water, and nutrients. They grow wherever it pleases — between sidewalks, along fences, behind garages, even through building foundations. Ailanthus reproduces rapidly, sending out root suckers and dispersing thousands of seeds carried by the wind. - Poisoning the Competition
Ailanthus releases allelopathic chemicals into the soil, suppressing the growth and germination of nearby plants. Maples, Pines, Black walnut, barley, and rye grains have similar capabilities.
The chemical ailanthone from Ailanthus altissima stops normal cell division in plant roots. It blocks the formation of spindle fibers that help align chromosomes during mitosis. Without proper spindles, the cells do not divide correctly. Ailanthone also makes cells leaky by weakening the membrane structure, upsetting the water and nutrient balance inside root cells. As a result, roots cannot absorb water properly, which can debilitate or kill adjacent plants. The compound shows promise as a natural herbicide, fungicide, and pest deterrent, but it is non-selective and toxic for commercial use. - Messy Tree
Ailanthus grows fast, but its wood is heavy and prone to storm and wind breakage. For property owners, that means falling limbs, cracked sidewalks, and constant cleanup of seed pods. - Stinky
The leaves and male flowers of the tree emit a strong, offensive, rancid odor, particularly noticeable during the summer months. - Spotted Lantern Fly
The Spotted Lantern Fly is a natural predator of the Ailanthus since both are from China. The insect has been causing havoc in the Eastern U.S. since 2014, when it first arrived in Pennsylvania. It has spread to many other states. Fortunately, Colorado has not yet been invaded by this destructive insect. The Tree of Heaven is the preferred host plant for this invasive insect. The insect seeks out Ailanthus trees as a food source and to reproduce. Some Eastern cities actively remove Ailanthus to slow the spread of the Spotted Lantern Fly. Click here for more information about this invasive tree insect. - Difficult to Remove
Ailanthus can add 3 to 6 feet of height per year in the early stages. In ideal conditions, these trees can grow to 80 to 100 feet tall with trunks ranging from 3 to 6 feet wide. They tend to grow over sidewalks, alleys, and fences, increasing the complexity and cost of stump removal. Simply cutting it down will not solve the problem — doing so triggers an explosion of new root suckers. Homeowners must vigilantly dig up or apply herbicide to any sprouts to prevent trees from regrowing.
How to Identify the Tree of Heaven
The tree looks very similar to the Rocky Mountain Sumac. The Sumac is native to Colorado. Below are some key characteristics of the Ailanthus tree.
- Compound leaves: Leaves are large, with 7-15 leaflets arranged along a central stalk.
- Distinctive bark: The bark is gray and smooth on younger trees, becoming rough and fissured with age.
- Smell: Beak a leaf. It stinks.
Denver Forester’s Stance on Ailanthus
The City considers the Tree of Heaven an undesirable species and explicitly discourages planting it. Property owners are responsible for removing or controlling trees when they begin to break sidewalks and alleys. The City recommends Honeylocust, Bur oak, and Hackberry for shade trees. All provide structure, beauty, and wildlife benefits without the invasive tendencies of Ailanthus. Got a large Tree of Heaven and need some advice? Ross Tree has been servicing the Denver metro area since 1978. We are experts in removing large trees in tight places. We would love to earn your business. Call 303-871-9121 or click here to complete a service request form.
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