ID corner: 3 (Putting some teeth into it)

I was out on a field trip in Rock Creek Park, and a question arose about common names for one of our nonnative viburnums, Linden Viburnum (Viburnum dilatatum) (an observation from Lake Fairfax Park). This plant is distressingly common in a couple patches along the trail leading from the Nature Center and Planetarium down to the creek.

Discussion of Linden Viburnum led to talk of Japanese Snowball (a/k/a Doublefile Viburnum) (V. plicatum), another nonnative that shares with Linden Viburnum two field marks: parallel leaf veins ending in teeth, and red fruits (maturing to blue-black in Japanese Snowball).

While it is true that Linden Viburnum is relatively more common in D.C. than Japanese Snowball, I have definitely seen both in Fairfax County, and probably Japanese Snowball in Rock Creek Park.

Which leads us to Guelder-rose Viburnum (V. opulus), which I have incorrectly identified in the past as Japanese Snowball in Reston. The leaf shape is quite different, but it’s easy to be distracted by the showy inflorescences ringed by sterile flowers, a trait common to both. It’s possible that the Reston shrubs were planted, since they’re just off blacktop paths near benches and frisbee fields.

Which is all to say that I fell into the rabbit hole of identifying tooth-leaved viburnums in the Mid-Atlantic, and as a result, I wrote up a brief comparison table: six nonnatives and five natives.

There is a native with sterile flowers, found in the mountains, Hobblebush (V. lantanoides).

A lot of what I have called V. dentatum (Arrow-wood, native) may actually be V. recognitum, recently raised to species rank. Weakley et al. write in the Flora of Virginia app:

Because [these two species]… were lumped in previous Virginia studies, the relative distributions, abundance, and habitats… are not entirely clear. It appears that their ranges are largely sympatric in the state and that specimens of intermediate morphology sometimes occur.

TL; DR: for our field trip: Linden Viburnum, pushy invasive in D.C., and the most often found.