Some links: 101

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.

ID corner: 2

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!

Field trip and workshop resources in the DMV

Here’s a roundup, somewhat Northern Virginia-inflected, of some organizations that run field trips in the mid-Atlantic.

Nature Forward is our standard-bearer. Workshops and camps for kiddos and families, walks focused on birds/geology/botany/etc., CEU-credited courses in lichens/spring wildflowers/conservation history/etc., overseas travel—something for everyone at nearly every level of expertise. NF is also an important advocate for protection of natural areas in the DC metro.

Some outfits mostly interested in birds:

Are you ready for some botany?

Maybe something a little more niche is your interest.

Or you’re looking for something more fast-paced than the naturalist’s shuffle.

The Washington metro is a mosaic of publicly-accessible, natural areas under several different jurisdictions. Check out individual parks and recreational areas for scheduled workshops, camps, and events.

*I know these organizations only by referral/search, not by firsthand field trip experience.

ID corner

I was on a discussion thread at iNaturalist for an observation of Aralia species in Catonsville, Md. The non-native Japanese Angelica Tree (A. elata) has been escaping from cultivation and is reported in several Maryland counties.

How to distinguish A. elata from the native Devil’s Walkingstick (A. spinosa) in winter? David Sibley’s guide says that A. elata is “less spiny,” but that doesn’t help very much.

markerFortunately, Maraea Harris of Meadowlark Botanical Gardens pointed out for me (we were on an invasives removal work day) a cultivated example of A. elata, specifically the variety “Silver Umbrella” with variegated leaves (in the growing season, of course).

somewhat spiny young stemolder stemYou can see that the younger stems (at left) are lightly armored, but the older trunks show only vestiges of their spines. This observation squares with a horticultural blog post from Milan Havlis.

Also of note: cultivars are grafted, and can revert to the wild type. I wonder how many of our escapes are from cultivars.

Some links: 87

Trees and the three-lettered insects that munch on them:

  • To protect Eastern Hemlock (Tsuga candensis) from the Hemlock Woolly Adelgid (Adelges tsugae) (HWA), researchers are exploring natural genetic resistance, biological controls, and forestry techniques: Gabriel Popkin.
  • Emerald Ash Borer (Agrilus planipennis) (EAB) is clobbering native ashes (Fraxinus spp.) in the eastern U.S. Could doomed trees be turned into commercially useful building materials? Yes, say Sasa Zivkovic and Leslie Lok.

Space Coast Birding and Wildlife Festival 2020: 2

I took a break from the birds to look at some specialties of Floridian flora with Jim Stahl. We walked the grounds of the Merritt Island NWR visitor center (some of the greatest hits had interpretive signs), as well as the oak hammock trail not far from there.

We learned some quick keys for distinguishing between two very common native palms: the shrubby Saw Palmetto (Serenoa repens) and the tree-sized, covered with “boots,” Cabbage Palm (Sabal palmetto). Saw Palmetto has flat fronds and those prickles, while a Cabbage Palm leaf has a central vein that causes the leaf to form a V, and an older leaf will split along this vein. Cabbage Palm also shows brown stringy bits. On a Saw Palmetto, the fronts radiate from the distal end of the petiole, while a Cabbage Palm is costapalmate: the petiole extends farther into a midrib, forming sort of a teardrop shape.

terminalaxillaryJim pointed out two myrsine species, Marlberry at left and “Rapanea” at right.

We saw far too many examples of the non-native invasive Brazilian Pepper (Schinus terebinthifolia), one of six species on the refuge’s hit list. The tree was in bright red fruit in January.

upsideundersideThe heavy, ruddy streaks of sori on Swamp Fern (Blechnum serrulatum) are quite distinctive.

interpretedFlorida has a very large fern with pinnae that suggest our local Christmas Fern; it’s Acrostichum danaeifolium. Perhaps now I can remember the back half of the scientific name of our fern, Polystichum acrostichoides.

coastal plain willowAnd a specialty willow, Salix caroliniana.


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.