Category: Botany

My VNPS chapter newsletter published two brief book reviews by me on topics botanical, the -pedia series from Princeton University Press and David J. Gibson’s Planting Clues.

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.

This month we on the FCPA EDRR team are on the lookout for non-native invasive Java Water Dropwort (Oenanthe javanica). Based on information from Pennsylvania agencies, B and I thought that we had relocated some extensive populations in a creek floodplain in Herndon, and we documented as such (for example, 166611987). However, other Invader Detectives have identified our plants as Water-hemlock (Cicuta maculata), and I am tending to agree.

I reviewed the descriptions of the two plants in Flora of Virginia. Since they’re in different genera, there’s no straightforward dichotomous key for the pair.

One clue that we had the native C. maculata is that the plants were coming into flower on 10 June. The Flora has May to August for Water-hemlock and July to August for Java Water Dropwort—but that’s hardly definitive for a plant that’s just getting established in the Commonwealth and with voucher specimens for only Fairfax and Arlington Counties. There are some described differences between the two plants with regard to the inflorescence and fruit, but how do you catch the invasive before it flowers?

So we have to go back to descriptions of the stem and leaves. Here’s C. maculata:

Perennial 6-18 dm stout, erect, caulescent, branched, glabrous. Leaves 10-30 × 8-26 cm, 2 or 3 × pinnately compound, ovate in general outline; leaflets 2-12 × 0.6-3 cm, lanceolate, acute to acuminate; petioles 0.4-3 dm [4-30 cm], sheathing.

Comments: Stems often mottled below with purple. [emphasis added]

And here’s O. javanica:

Perennial with fibrous roots. Stems 3-12 dm, decumbent [reclining on the ground but with an erect or ascending tip], rooting at lower nodes. Leaves alternate, sometimes basal with petioles 5-10 cm, blades 3-20 cm long, ovate to triangular, 1 or 2 × pinnately compound, reduced upward, ultimately becoming sessile on expanded sheaths; leaflets 10-50 × 5-20 mm wide, ovate or rhombic-ovate, rounded, narrowed or tapered at base, serrate.

In other words, they’re both pretty typical members of the Carrot Family. Overall, the Water-hemlock is taller, with larger leaves, but there’s a lot of overlap.

Two things that we overlooked in our survey of the Herndon site:

• O. javanica stems are decumbent, whereas the plants in our observations are erect.
• “Brittle stems of java waterdropwort are jointed and hollow and can easily break off and take root.” I don’t believe that we checked our specimens for this character.

Since O. javanica is reported to be edible (it has common names like Water Celery and Vietnamese Parsley), it’s a good thing that we didn’t give our plants a taste!

Lantana strigocamara, sometimes cultivated as a street planting, is only the sixth plant known to produce blue fruits through structural color, rather than pigment.

Rory Hodd looks at liverworts.

Jökla-mýs (glacier mice) are neither glaciers nor mice. Nor are they tribbles. Discuss.

Some wildflower species don’t need organics in the soil to thrive, and don’t need what we would call hospitable temperatures. Rachel Cohen of Boise State Public Radio takes a botany walk through Craters of the Moon National Monument and Preserve, which has 750 species on its checklist.