Tree of Heaven: The Invasive Plant Taking Over Our Hillsides

You may have spotted this plant on a recent walk: it's Tree of Heaven (Ailanthus altissima), one of the most aggressive invasive trees in California. You can usually tell it apart from our native trees by its long compound leaves, each with a dozen or more smooth-edged leaflets, and by the strong, unpleasant smell the crushed leaves give off (some people compare it to rancid peanut butter).

Photo: Isaac Golino

Tree of heaven grows fast, spreads by both seed and root suckers, and releases chemicals into the soil that suppress the native plants around it. The biggest mistake people make is cutting one down on its own: without a follow-up herbicide treatment, a cut tree responds by sending up a thicket of new sprouts from its roots, sometimes fifty feet from the original trunk. That's why removal on parkland like ours needs to be coordinated with LA Recreation and Parks and done by a licensed applicator, not handled tree-by-tree by volunteers.

What you can do: if you spot a seedling like this one, small enough to hand-pull with its root intact, go ahead and pull it before it has a chance to establish. For anything larger, please don't cut it yourself.