June 8, 2010

This strikingly handsome purple-leaved small tree with wispy flowers is found on the south side of the W&OD bike path immediately west of the American Dream Way bridge.  There are several more specimens in the median between the W&OD bike path and the W&OD gravel path near the Fannie Mae Gardens.

This is a smoketree (Cotinus coggygria, see this Virginia Tech fact sheet, NC State fact sheet and this Wikipedia article), which is a relative of the sumacs

In a clearing south of the W&OD bike path across from the Fannie Mae Gardens is a thicket of this plant, whose flower resembles a small thistle but whose leaves and stems are far less spiny.  This appears to be a knapweed (Centaurea spp.), and may be the highly invasive spotted knapweed (C. maculosa, see this Missouri description and this Wikipedia article).

Pokeweed (Phytolacca americana) is beginning to bloom, as here on the north side of the W&OD bike path near Isaac Newton Square;  see this post from last September for how pokeweed appears once it fruits out.

 A couple of small flowering plants hidden in the grass west of the W&OD bike path south of Sunset Hills Drive.  The white five-petaled flower with prominent anthers appears to be Carolina horsenettle (Solanum carolinense), already featured before in this post from last October.  The small pink-flowered plant next to it with the reddish stem and comparatively large lanceolate leaves appears to be some form of knotweed, perhaps tufted knotweed (Polygonum caespitosum, compare this Virginia Tech weed guide and this Connecticut description), even though the Digital Flora of Virginia does not list this species.

No doubt about this species - this is common milkweed (Asclepias syriaca), now bursting into flower in this thicket on the south side of the W&OD bike path across from the Fannie Mae Gardens.

Close-up of an inflorescence.  Compare the Missouri description.

Milkweed flowers are apparently quite popular with insects.  Here is a shot with two large butterflies feeding on separate inflorescences;  these plants are located in the median between the W&OD bike path and the W&OD gravel path just south of Sunset Hills Drive and north of the Dulles Toll Road bridge.

And here is a shot with a bee of some sort.

Late afternoon on September 21, 2009

Winged or shining sumac (Rhus copallina) in the weedy strip separating the parking lot for 1801 Robert Fulton Dr from the W&OD bike path.  Note the shiny wings along the petiole that joins the 11 leaflets in the compound leaf at the lower left.  For more on this species, see Virginia Tech tree factsheet.

The clusters of drupes on this sumac can get quite large.

Another shining sumac in the same strip, this one without the obvious clusters of drupes, but showing splotches of deep red fall coloration appearing.

In this particular weedy strip the pokeweed (Phytolacca americana) can get quite tall!

This strip also contains a large number of grasses, which add considerably to both the biodiversity and the beauty of this habitat.  This particular grass appears to be green foxtail (Setaria viridis), based upon its height, size and shape of panicle, drooping habit, and absence of hairs on the leaves;  see Virginia Tech weed guide.

Another view of a panicle from this grass, which is found quite frequently along this stretch of the W&OD bike path.

Mile-a-minute weed (Persicaria perfoliata) patch near the junction of the W&OD gravel path and bike path just south of the underpass under the Dulles Toll Road.  Note the distinctively shaped leaves (equilateral triangles), the round collars (ocreae) around the stem underneath some of the green fruit (especially in the lower center of the picture), and the bright blue color of the ripening fruit.  This is a highly invasive species;  see the National Park Service fact sheet.

Another view of this patch of mile-a-minute weed, with the prominent triangular leaves and a good example of an ocrea just underneath the blue fruit in the middle of the picture.  This particular patch has already climbed over some of the adjoining shrubs;  elsewhere along this stretch of the W&OD, mile-a-minute weed appears to be mostly a ground-hugging vine.

Cattail or bulrush (Typha latifolia) growing in a drainage ditch along the W&OD gravel patch underneath the Dulles Toll Road overpass.  I found this Wikipedia article on Typha to be informative.

A closer look at the distinctive cigar-shaped inflorescence of the cattail.

Morning of September 21, 2009

Leaves (with their characteristic fan shape) emerging from the trunk of a gingko tree (Gingko biloba), planted near the edge of the soccer field southwest of the intersection of Sunrise Valley Drive with Barton Hill Road.  There are two gingkos here;  the only other ones I have seen so far in Reston are in the parking lot at the Plazamerica shopping center.

Branch of an Eastern hemlock tree (Tsuga canadensis), located on the pathway between Villaridge condo complex and Thoreau Place just across South Lakes Drive from South Lakes shopping center.  Note the older cones on the lower left that are brown and opened, while the newer cones on the upper right are still green and closed.

A better look at one of the new green cones on this hemlock.  If you click on the picture for a higher-resolution version, you can see the two parallel white stripes of stomata on the undersides of the needles that are a hallmark of hemlocks.  Also noticeable in this picture is that the needles taper from their base to their tip;  according to the Virginia Tech tree datasheets, this is what best distinguishes Eastern hemlock from Carolina hemlock.

A cluster of red berries on a flowering dogwood (Cornus florida) at the southwest corner of Sunrise Valley Drive with Barton Hill Road.  Like many of the flowering dogwoods in Reston, this one is suffering from disease (I am not a plant pathologist, and thus cannot diagnose the specific disease that is burning this tree's leaves).

Pokeweed (Phytolacca americana) in a weedy patch along Sunrise Valley Drive just east of the Barton Hill Road tennis courts.  Note the characteristically purple stem, which can become quite thick in the fall, as well as the clusters of berries that are turning from green (near top of picture, bleached by the camera flash) to dark purple.  These berries are quite poisonous.  Compare the description at the Virginia Tech weed guide.