Early Afternoon of September 4, 2010

At the northeast corner of the small parking lot that is itself in the northeast corner of the intersection of the W&OD bike path with Old Reston Avenue is this tree with opposite pinnately compound leaves (with around 7 finely serrate leaflets) that now bears large clusters of greenish single-winged samaras.  This is an ash (Fraxinus spp.).  According to the Digital Flora of Virginia, the ash species found in Fairfax County are the white ash (F. americana, see the Virginia Tech ID sheet), the green ash (F. pennsylvanica, see the Virginia Tech data sheet), and the pumpkin ash (F. profunda, see the Virginia Tech fact sheet).  I am not yet able to decide which of these my specimen here is.

Just opposite this parking lot, as well as a bit further east on the south side of the W&OD bike path, one finds this plant that is now profusely orange-flowering, with the cup-shaped flower having a distinct spur that almost gives it the appearance of being an old-fashioned pipehead.  The leaves are broadly serrate (the triangular leaves in this image belong to mile-a-minute vine, which is a noxious weed infesting the entire W&OD bike path roadside in Reston).

Another image of this plant, giving a better view of the leaf with its distinctive serration.  This is orange jewelweed (Impatiens capensis, see this Illinois description and this Missouri description).  I guess I'll have to look out for the seeds to appear and then test whether they in fact eject explosively when touched!

All along the southern edge of the W&OD bike path east of Old Reston Avenue the ragweeds (Ambrosia spp.) are in full bloom, ready to release the pollen that is such a bane for allergy sufferers.

This particular specimen has unlobed to trilobed leaves, as seen here, which, together with its substantial height (the racemes extend above my height), makes this giant ragweed (Ambrosia trifida, compare this Illinois description and this Missouri description).

A bit further east along the W&OD bike path is this specimen, whose flowers are already tinged yellow and thus just about ready to release their pollen.  The leaves on this specimen are pinnately lobed, but not quite bipinnately compound, which suggests that this is western ragweed (Ambrosia psilostachya, see this Texas description) rather than common ragweed (A. artemisiifolia, see this Virginia Tech weed description and this Illinois description), which I also saw today but failed to photograph.

The silky or Chinese bush clover (Lespedeza cuneata) is now in bloom, bearing small white flowers that look much like pea flowers (understandable given that, like peas, vetches, black locusts, wisteria, and other clovers, this is a legume).  For how the bush clover looked a couple of months ago as it first emerged from the ground, see this post from June;  for how it will look in a month once it bears its fruit, see this post from last October.

Another legume that is now profusely blooming (purplish-pink rather than white), as seen here on the south side of the W&OD bike path just west of Isaac Newton Square, is the tick clover (Desmodium spp.).

A closer look at some of the tick clover flowers.  In the lower right corner of the image, one can also see some fruit, which in this genus typically is in the form of four seeds that are individually encapsulated along a string rather than contained in a pod.  For some descriptions of tick clover, see this Missouri description and this Illinois description.  There are quite a few species of this genus found in Fairfax County, and they are difficult to tell apart, so I cannot provide specific identification for this plant.

One more legume, this one in tree form.  This honeylocust (Gleditsia triacanthos, see this Virginia Tech fact sheet) is located on the southern edge of the Pizza Hut parking lot adjoining the W&OD gravel path just east of its intersection with Wiehle Avenue.  One can easily see the pinnately compound leaves with dozens of small roundish leaflets that are typical of legumes (for example vetches or black locusts).  Looking closer (especially near the right edge of the image) one can also see the twisted remnants of large seed pods.  The resilient honeylocust is a popular ornamental tree for parking lots and other highly polluted areas (such as the parking lots for Plazamerica and for the Spectrum Center);  most of the ornamental honeylocusts planted now are sterile, but this one is not and thus actually produced seed.

June 22, 2010

This tall, narrow, single-stemmed plant with trifoliate compound leaves is now sprouting up like crazy along roadsides and in grassy areas.  It is a form of bush clover (Lespedeza spp.) and, based upon the pointy spike at the end of each leaflet, appears to be the highly invasive silky or Chinese bush clover (L. cuneata, for which see this Illinois description and this Missouri description).  For how this plant looks in the fall after going to seed, see this post from last October, where I misidentified it as Scotch broom, a related trifoliate legume (this did not burst into yellow flower in spring as predicted;  as a matter of fact, the plants have really emerged only in the last month or so).

This tall spindly plant with tiny white flowers can be found north of the W&OD bike path between Isaac Newton Square and the driveway for the Oak Hill Christian School.  It is white sweet clover (Melilotus albus, see this Missouri description), yet another highly invasive trifoliate legume.

At the edge of the parking lot for 1801 Robert Fulton Drive, just south of the picnic area for the W&OD bike path, is this unassuming cluster of yellow eight-rayed flowers with very wiry leaves that are whorled around the stem.  This appears to be thread-leaved tickseed (Coreopsis verticillata), for which see this Floridata record.

In the median between the W&OD bike path and the W&OD gravel path just south of Sunset Hills Road is this small meadow of gently swaying perennial ryegrass (Lolium perenne, see this Missouri description and thisOregon State treatise), just developing its inflorescence.

On the north side of the W&OD bike path just west of its intersection with Wiehle Avenue one can find this milkweed (Asclepias spp.).  It has rather narrower leaves than the common milkweed (A. syriaca) found elsewhere, and its inflorescence is at the apex of the plant, rather than hanging from its shoulders.  This appears to be swamp milkweed (A. incarnata, for which see Missouri description and this Illinois description).

The sumac (Rhus spp.) are now in bloom, as here on the north side of the W&OD bike path between Isaac Newton Square and the driveway for the Oak Hill Christian School.  This particular specimen is not the winged or shining sumac (R. copallinum) found more commonly around here (the leaf lacks the characteristic wings; compare this post from last September), but instead is smooth sumac (R. glabra, for which see this Virginia Tech fact sheet).

Further west, on the south side of the W&OD bike path just east of Old Reston Avenue, this sumac is already breaking out into fruit.  I wasn't able to quite get close enough to see what kind of sumac this is.

And finally, a nice illustration of how morning glories come by their name.  This is the same specimen of wild potato vine (Ipomoea pandurata) featured in this post from last week.  But whereas that picture was taken at 10 a.m., while the funnel-shaped flowers were at their peak opening, this picture was taken around 5 p.m. and shows the flowers rolled up against the day's heat.

October 8, 2009 (continued)

On the east side of the W&OD gravel path, just north of the Dulles Toll Road bridge, is this rather strange plant that looks like it ought to be a grass of some sort, but is not (it has really short rather than long leaves).

A closer look at some recumbent branches.  Note the quite small trifoliate leaves with entire leaflets. I believe this is Scotch broom (Cytisus scoparius), which would make the brown structures seen in the image the remnants of burst seed-pods.  Compare this Virginia Tech fact sheet and this Forestry Service description.  If I am correct in this identification, then there should be bright yellow flowers next April to June, making it look similar to a forsythia.

Added by edit June 29, 2010:  this did not bloom yellow.  Instead, I now believe this is silky or Chinese bush clover (Lespedeza cuneata).