Ailanthus altissima tree of heaven

Female Ailanthus altissima adorned in terracotta-red samaras that echo the warm brick and roof tiles of Alma Street, Palo Alto. Sairus Patel, 8 Aug 2018

Female Ailanthus altissima behind Haus Mitteleuropa. Sairus Patel, 18 Jul 2021

Like the glossy privet, tree of heaven is a shapely tree of undeniable beauty, yet much maligned for its by-now legendary invasiveness. Long, pinnately compound leaves droop gracefully, and can be told at once from those of our native walnut and similar trees by the pair of coarse gland-tipped lobes at the base of the leaflets and by their sharp, garlicky smell when crushed. Scratch the bark and you get this same scent, a fact well known to the volunteer ailanthus-removal crews who work the local creeks in winter after leaf-fall.

Some don’t mind the yeasty odor of the clusters of small flowers on male trees; others insist they reek to high heaven, and are, curiously, more vocal about it than the former group. This distaste once led, when intentional planting still occurred, to the use of female trees only. On such trees, clusters of greenish-yellow samaras mature through apricot to a rich terracotta red by mid-summer, layers of color present at once, producing a glorious spectacle for months, as can seen on the full-canopied standalone examplars on Alma Street at the downtown Palo Alto train station. Not bad for unwatered trees rooted in hardpan, rising from two-foot-wide slots in the concrete and faithfully shading commuters’ cars in a stark parking lot for decades. Nearby, feral ailanthus run in bands along the tracks, and should be a familiar sight to train passengers. “It will grow where all else fails. And it’s better to have an ailanthus than nothing,” said Howard Irwin, Executive Director of the New York Botanical Garden, in the 1970s, likely inspired by Betty Smith’s 1943 book A Trees Grows in Brooklyn. Today, that might not be the consensus, but it shouldn’t dull our marvel at its grit and grace.

On central campus, two large specimens remain, both female, behind Phi Kappa Psi (592 Mayfield Avenue) and Haus Mitteleuropa nearby (620). A giant at the southeast corner of the Kingscote Gardens building was lost to re-landscaping in 2015. A few palm-like suckers spring up in the Arboretum north of the Mausoleum now and then. A resplendent multi-trunked tree persists in the parking lot south of the Stanford Arboretum Children’s Center.

Ailanthus altissima samaras. John Rawlings, 23 Sep 2006

Name der ivation: Ailanthus – Latinized version of the native Moluccan word ailanto (sky tree) for a species of this genus; altissima – tallest.