It's not Poison Ivy

As I was surveying which native species were growing successfully under my Norway Maple (for a future blog post), I came across many seedlings with ‘leaves of three.’ I thought, #Golly#, Poison Ivy! On closer examination, I realized that these were growing as individual plants, not a vine and the leaf shape, with its entire, unlobed margins, just wasn’t quite right for poison ivy. After checking some field guides and looking for similar plants growing in the area, I found out that these were seedlings of Wafer Ash, Ptelea trifoliata. The parent plant was growing behind the garage in an area I rarely paid any attention to.

Wafer Ash, also known as Hop Tree or Stinking Ash, is native to the Southeastern and Midwestern States, its native range does not extend up to Massachusetts, but it is listed as hardy to zone 5A.  I’m not sure how this tree got into my yard.  It’s not commonly used in the landscape trade and with a name like ‘Stinking Ash’ it’s not likely to be popular.  This name refers to the musky odor of its bark and leaves when crushed.  In this case, the name is a bit deceiving; I find that, while not pleasant, it does not smell as bad as something like wild Black Cherry.
Wafer Ash grows as a large shrub or small understory tree with irregular branching, usually growing to about 20 feet in height. The seedlings put down a tap root that can make them difficult to pull up.  It is native to dry rocky uplands and is very tolerant of shade. These two features make it suitable for growing under a Norway Maple, with its dense network of thirsty roots and dense shade canopy. Wafer Ash prefers neutral soils and is listed as deer highly resistant and tolerant of salt and ‘mine spoils’. The only conditions it does not tolerate are soil compaction and flooding.

This tree blooms in early to mid-June in the Boston area with terminal clusters of yellow-green, sweet smelling flowers. (Some sources list flower scent as unpleasant, but I found it quite nice and detectable several yards away.) The tree serves as a larval host for Eastern Tiger Swallowtail and Giant Swallowtail butterflies and is generally attractive to birds and pollinating insects. For more photos and information check out this link to the Wildflower Center.

The name ‘Hop Tree’ refers to its use in earlier times as a hop substitute in the brewing of beer. The dried seed pods (samara) can be decorative. My experience under the Maple and elsewhere in my yard is that these seeds high viability and offspring can appear just about anywhere. I don’t know if their spread is a result of being blown around naturally or from being caught up and thrown around by the lawn mower.

In my experience, the Wafer Ash is an excellent North American native understory tree with high wildlife value for dry, shady conditions. While it not commonly available in the landscape trade, there are a few commercial sources. Lacking that, I’ve got a bunch growing in my backyard. (You can reach me through the Adams Garden fan page on Facebook.)