Afternoon of September 25, 2009 (continued)

Overview shot of a large chestnut tree located just east of Reston Parkway on the south side of Bowman Green Drive, which is the circular approach to an early-to-mid 20th century mansion built for the owners of the large farming estate on which the Reston development originated in the 1960s.  I believe this is a Chinese chestnut (Castanea mollissima);  more on identifying characteristics below.  There is another chestnut (somewhat less grand) on the exact opposite side of Bowman Green Drive.

A colleague at work alerted me to the fact that this chestnut is now in full fruit.  Compare with the Virginia Tech fact sheet.

Once the burr-covered fruit ripen and fall from the tree, they will pop open to reveal nuts inside (the nuts here have apparently already been snacked away by the local fauna).  The burrs are huge - see the keys for scale.

View of another fruit-laden branch.  Note also that the undersides of the leaves are much paler than the top sides.  According to this site, this is one of the distinguishing characteristics of Chinese chestnuts as opposed to American chestnuts (Castanea dentata).

A closer look at the underside of a leaf.  Note the relative sparseness of the teeth.  Note also that the very base of the leaf is rounded, so that it meets the vein at roughly right angles rather than at a much sharper angle.  These, too, are characteristics of Chinese chestnuts.  However, as pointed out by this director of the New York Chapter of the American Chestnut Foundation, there has been extensive hybridization among Chinese, American, and European chestnuts over the past two centuries, so the boundaries between the species are no longer very sharp.

Two trees to the east of the chestnut tree on the south side of Bowman Green Drive is this gorgeous river birch (Betula nigra), with its flaking red-orange bark.  Compare the Virginia Tech fact sheet.  According to the key in Richard J. Preston, Jr., and Richard R. Braham, North American Trees, 5th edition (2002), p. 170, river birch is one of only two birches that exfoliates reddish (as opposed to white) bark, and the other (yellow birch, B. alleghaniensis) can be distinguished based on leaf shape.  This type of river birch can be found on both sides of Reston Parkway (for example right outside the Macaroni Grill on the northwest corner of the intersection with New Dominion Parkway, and behind the On the Border Mexican Restaurant in the Spectrum shopping center).  Although river birch is native in this area, these are clearly ornamental plantings, as Reston Parkway is on a ridge rather than in a bottomland, which is the normal setting for these birches.

Closer look at the leaves of this river birch, showing them to be untoothed and wedge-shaped at their base.  Also noticeable in this photo are three green protrusions from the end of the twig.  In birches, male flowers are "preformed", that is, they develop during the fall and remain on the tree throughout the winter until the female flowers emerge in the spring.  I wonder whether these are the beginnings of three male catkins.

Acorns in what I believe to be a pin oak (Quercus palustris) on the west side of Reston Parkway just north of its intersection with Bowman Towne Drive.  Compare the Virginia Tech fact sheet.

Some more acorns in this tree.  The acorns are rather short and stubby, and thus are not Northern red oak (Quercus rubra - see Virginia Tech fact sheet).  Also, the cup appears to my eyes to be saucer-shaped rather than bowl-shaped, which means it is not scarlet oak (Quercus coccinea - see Virginia Tech fact sheet).  Pin oaks are ubiquitous in Reston.

Tall ornamental juniper shrub next to the Chevy Chase bank in the extreme southeastern corner of the Spectrum shopping center.  According to Melanie Choukas-Bradley, City of Trees, The Complete Field Guide to the Trees of Washington, D.C. (3rd ed., 2008), pp. 142-143, the juniper that is by far most commonly encountered around here is the Eastern redcedar (Juniperus virginiana).  Compare with the Virginia Tech fact sheet.

A close-up of this juniper, with the colors somewhat bleached due to the camera flash.  Note the small, closely appressed, scale-like leaves, as well as the round, blueish, berry-like cones - both of these characteristics appear consistent with this being an Eastern redcedar.

Right next to the juniper (which can be seen in the background here) is this ornamental cherry tree (Prunus spp.).  Without flowers I cannot identify the cherry more specifically.  But this tree nicely shows the very distinct horizontal ringing of the bark that makes cherry trees (as a genus) easily identifiable at any time of the year.  Compare this Virginia Tech fact sheet.

A closer view of the shiny bark on a side trunk of this cherry tree.  The distinct horizontal layering is caused by abundant horizontal lenticles, which are openings in the bark through which the tree can exchange water and gases.

One of a line of willow oaks (Quercus phellos) planted along the east side of the Barnes & Noble parking lot adjoining Reston Parkway.  Compare this Virginia Tech fact sheet.

Even though the leaves are willowy-slender and not lobed like other oak leaves, this is still an oak, as can be seen by the presence of acorns (see the three hanging in the middle of this picture).  Note that the acorns are very similar to those of the pin oak (Q. palustris), but the leaf shape of course is very different.

Along the south side of Temporary Road east of Old Reston Avenue is a line of about 5 beautiful ornamental pines.  They have fascicles of two long needles each, so they could be cultivars of Austrian pine (Pinus nigra, compare Virginia Tech fact sheet), Japanese black pine (Pinus thunbergii, compare Virginia Tech fact sheet), or Japanese red pine (Pinus densiflora, compare Virginia Tech fact sheet).  I just love the triangular symmetry of cones and buds on these pines!

Close-up showing a mature cone (which has developed from the female flower) on top and the remnants of male flowers below it.

What I believe you have in this shot are green cones below, which were pollinated this past spring but have not yet been fertilized (it apparently takes a year or so for pollen inside a pine cone to actually fertilize), and new female flowers starting to bud at the top.

Further east on the south side of Temporary Road, at the very northwestern corner of the Temporary Road Recreation Area, is this common persimmon (Diospyros virginiana) in full fruit.

Watch out when stepping underneath this tree!  Once the ripe fruit has fallen (some can be seen in the grassy area), it becomes rather mushy, and when stepped on it leaves behind a big purple splotch, as seen on the sidewalk.

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.