Tree of Heaven Identification: Leaves, Smell, Look-Alikes

Look at the edge of one leaflet: a tree of heaven leaflet is smooth all the way round except for one or two small bumps, called glandular teeth, near its base, and a crushed leaf smells strongly unpleasant. Penn State Extension and Purdue Extension both put those two features first. The full checklist:

• Compound leaves. One long stalk carrying many leaflets: 10 to 40 by Penn State's count, 11 to 41 by Purdue's. The whole leaf is 1 to 4 feet long (Penn State).
• Smooth leaflet edges with glandular teeth at the base. This is the single best field mark (Penn State).
• One leaflet at the tip. Purdue notes a single terminal leaflet.
• The smell. Purdue compares it to rancid peanut butter; Penn State to cat urine or burnt peanut butter. The pith of a snapped twig smells the same (Penn State).
• Bark. Smooth and light grey with lenticels on young trees, developing fissures with age (Purdue); Penn State likens the pattern to cantaloupe skin.
• Growth habit. Fast-growing, often in clumps or colonies that spread from roots (Penn State), and able to sprout in pavement cracks and building foundations (Purdue).

Without leaves, go by twigs, scars and seeds. Penn State describes stout, greenish-brown twigs with alternate branching, large V- or heart-shaped leaf scars, and a large spongy brown pith that smells as bad as the leaves when a twig is snapped. Female trees keep clusters of twisted, winged seeds, 1 to 2 inches long, on the branches through winter (Penn State). Tree of heaven is dioecious, so a male tree will not have them.

Sumac, black walnut and hickory are the usual mix-ups, and Penn State gives one rule that separates all three: their leaflet edges have teeth (serrations), while tree of heaven leaflets are smooth apart from the glandular teeth at the base. Details that help:

• Sumacs. Wikipedia says the lobed bases and glands on the leaflets separate tree of heaven from similar sumac species. Sumac leaflets are toothed along the edge (Penn State).
• Black walnut. Fewer leaflets, 15 to 23 by Purdue's count, with toothed edges, and no rancid smell. Penn State pairs black walnut and staghorn sumac as native trees to learn alongside it.
• Hickories. Toothed leaflets (Penn State).
• Ash. Ashes also have compound leaves; see our ash tree identification page for how to recognise them.

If you are unsure, crush a leaflet. Penn State notes that the foul odour is absent in the look-alikes.

• Seeds. Penn State says a female tree can produce more than 300,000 seeds a year; Purdue says hundreds of thousands.
• Root sprouts. Sprouts can come up as far as 50 feet from the parent tree (Penn State), which is how one tree becomes a thicket.
• Spotted lanternfly. Purdue calls tree of heaven a preferred host of this invasive insect.
• Legal status. In Indiana it is on the Terrestrial Plant Rule, in effect since 2019, which makes it illegal to sell, gift, barter, exchange, distribute, transport or introduce (Purdue). Check your own state's list.
• How it got here. Wikipedia records that gardener William Hamilton brought it to Philadelphia in 1784; Penn State says the late 1700s. Wikipedia lists it from Massachusetts west to Iowa and south to Texas, and in the West from New Mexico to Washington.

Not by cutting alone. Penn State warns that a cut or injured tree of heaven may send up dozens of stump and root sprouts, so felling it usually makes the problem bigger. Penn State's approach is to kill the root system with herbicide first:

• Timing. Mid- to late summer, from July until fall colour, when the tree is moving carbohydrates down to its roots.
• Hack-and-squirt. Downward-angled cuts into the trunk with herbicide applied to them, leaving uncut bark between them so the chemical travels to the roots.
• Basal bark. For stems up to 6 inches across, concentrated triclopyr applied from the ground line to 18 inches up.
• Foliar spray. A glyphosate and triclopyr mix for sprouts and small stems.

Cut the dead tree afterwards if needed. Follow the herbicide label and local rules, and for a large tree near buildings or power lines, a licensed arborist or applicator is the safer choice.

Penn State lists dermatitis from contact and, rarely, myocarditis among the health concerns, and notes that the pollen causes allergies in some people. Wikipedia reports rare myocarditis cases in workers clearing heavily infested areas, linked to sap exposure. When cutting or pulling it, wear gloves, long sleeves and eye protection, and wash exposed skin afterwards. If you develop a rash that spreads, chest pain or shortness of breath after working with it, see a doctor and mention the plant.

None of the sources we opened ranks a single tree as the most invasive in the country, so we will not name one. What they do say about tree of heaven is enough to take it seriously: Purdue calls it a widespread invasive pest, Wikipedia lists it across much of the lower 48 states, and its seed output and root sprouting (above) are why it spreads so fast. Your state's invasive plant list is the best guide to which trees are the local priority.

PlantLens can suggest a name from a photo. For tree of heaven, photograph a whole leaf and then a close-up of the base of one leaflet so the glandular teeth show. Confirm with the smell test before you treat or remove anything, because the native look-alikes are worth keeping. For more on trees, see identifying trees by leaf and identifying trees by bark.

Research and drafting for this page were done with the help of AI, and every figure was then checked line by line against the sources listed at the end. Where sources disagree, we say so rather than pick one silently. If you find a mistake, tell us and we will correct it.