Acer negundo box elder

Acer negundo ‘Variegatum’ near the Clock Tower. John Rawlings, c 2006

An unusual maple in that its leaves are trifoliate, or pinnate with up to 7 leaflets, resembling those of the elderberry (hence “elder” in the name). “Box” refers to the wood once being used to make boxes. One of North America’s most widespread trees, fast-growing and sometimes weedy, it has a reputation for being structurally unstable and prone to decay.

A large, sprawling exemplar is behind Xanadu (558 Mayfield Avenue), but the most conspicuous campus trees are a trio of the more petite ‘Variegatum’ in an island on Escondido Mall just east of Meyer Green. The white-edged leaves are tinged pink when new, and the prolific strings of samaras are likewise pink at first. (The species is unusual among maples in having reliably separate male and female trees.) Occasionally a shoot reverts to green leaves; it is usually removed before it can dominate.

These are a remnant of an extended planting theme along the mall that began with a similar trio near the Clock Tower and later continued with another just east of Meyer Green. The other trees were removed during redevelopment of the School of Education in the early 2020s.

A form wth downy leaves, sometimes treated as subspecies californicum, occurs locally along stream edges, including at Jasper Ridge. A much reduced specimen forms part of a screen planting on the right at 2150 Oberlin Street in Palo Alto.

Linnaeus noted an earlier author’s observation that this North American maple was being confused with Vitex negundo, the species from India (and elsewhere) that also features 3-to-5-part leaves. The epithet negundo – from the Sanskrit name for the plant, nirgundi (“without disease”) – properly belongs to the vitex, valued for its medicinal uses. Linnaeus assigned negundo to the maple as an enduring reminder of this historical mix-up, while correctly recording that its leaves were in fact ash-like – pinnate rather than palmate, as in the vitex.

Illustrations: samaras | leaf of A. negundo var. californicum, whose leaflets are densely hairy beneath | Jasper Ridge photo archive.

Acer negundo leaf and samaras. From Trees of Stanford and Environs, by Ronald Bracewell