Tuesday, September 22, 2009
Late afternoon on September 21, 2009 (continued)
Close-up of the flowers of late-flowering thoroughwort, also known as late-flowering boneset (Eupatorium serotinum), along the side of the W&OD bike path just south of the Dulles Toll Road. Compare the description of this common roadside weed at this cool site on Missouri plants and this nifty site on Illinois wildflowers.
Another view of the flowers in this plant, which occur as small disk flowers in umbels, or rather flat-topped aggregations. Note the insects noshing away!
A view of the plant as a whole. I found this useful key to nine of the more common Midwestern Eupatorium species from the Field Museum of Natural History in Chicago. On this key, my specimen clearly keys out as Eupatorium serotinum - leaves are opposite, flowers are white, leaves are petiolate (with a stem), not sessile (attached directly to the stem) or perfoliate (wrapped around the stem), and the leaves are definitely lanceolate. The Digital Atlas of Virginia Flora lists a total of 17 Eupatorium species as occurring in Fairfax county. Six of these are on the Field Museum key, and according to the Checklist of Washington-Baltimore area flora two more are mere synonyms and a third is represented by a single 1899 report. Of the remaining eight, E. rotundifolium has ovate leaves, E. pilosum, E. leucolepis, and E. album have sessile leaves, E. hyssopifolium has much smaller leaves, E. godfreyanum is a hybrid of E. rotundifolium and E. sessilifolium, E. dubium has purple flowers, and E. capillifolium has deeply dissected leaves. Thus, it appears that by process of elimination this can be confirmed as E. serotinum.
A shrub of autumn olive (Elaeagnus umbellata), bearing abundant bright red berries, just north of the Dulles Toll Road on the W&OD bike path. Autumn olive is extremely common along the W&OD in Reston. It is highly invasive; see, for example, this National Park Service sketch.
A closer view of berries on an autumn olive shrub right at the Dulles Toll Road bridge. In the higher-resolution version of this picture, you can still see some speckling on the fruit. As mentioned in this USDA fact sheet, there is a related invasive species, Russian olive (E. angustifolia), whose berries are somewhat larger, more oblong, and drier than those of autumn olive. These berries here are definitely round and juicy!
A persimmon tree (Diospyros virginiana) bearing fruit, on the W&OD gravel path about 100 feet north of Sunset Hills Road. There are two fruit-bearing persimmons about 50 feet apart at this location, and I know of one other persimmon along Temporary Road near North Shore Drive. Compare the Virginia Tech tree fact sheet and this Wikipedia article. The fruit are already ripe and dropping, so that one has to watch where one steps on the path near here!
Close-up view skywards of a summer grape (Vitis aestivalis) vine, which is also bearing abundant fruit now. This particular specimen is located on the W&OD bike path at the peak of the hill between Sunset Hills Road and Michael Faraday Court. Note the toothed, heart-shaped leaves and the curly tendrils; compare with this Virginia Tech tree fact sheet. Summer grape is found very extensively along the W&OD path in Reston and frequently covers and smothers small trees; definitely the most prominent vine around here!
A little bit closer to Michael Faraday Court on the W&OD gravel path one finds this location, where a summer grape vine has draped itself over an autumn olive shrub. Both plants are in full fruit, making for this nice juxtaposition of red and blue berries. The mixture sounds positively Mediterranean; however, the autumn olive is not related to the true olives found in Italy and neighboring countries.
A nice view of mature cones at the end of a branch of Eastern white pine (Pinus strobus), on Wiehle Avenue north of the W&OD path. Eastern white pine is very widely planted in Reston and is one of our dominant tree species.