Afternoon of October 19, 2009

After 5 days of rain, finally a sunny fall day!

These are the field thistles (Cirsium discolor) that are between the W&OD bike path and W&OD gravel path just north of the Dulles Toll Road bridge.  For pictures of them in flower almost three weeks ago, see this post.

Now the thistles have gone to seed, with the seeds located at the bottom of tufts of long white hair that will carry them away with the wind.

Along the W&OD bike path between Sunset Hills Road and Michael Faraday Court one frequently encounters sassafras (Sassafras albidum) in the understory.  These trees are easily identified by their trident-shaped leaves.  Compare the Virginia Tech fact sheet.  The leaves are now beginning to turn to attractive yellows to reds.

Here is an earlier view of an understory sassafras tree along the W&OD bike path just north of Sunset Hills Road taken exactly four weeks ago.

On the north side of the W&OD bike path just west of Michael Faraday Court there is a stretch of about 20 feet where one will encounter frequent specimens of this grass.  From Lauren Brown's Grasses:  An Identification Guide, I believe this is rye (Secale cereale) and not one of the native wild ryes (Elymus spp.), because the head of fruit has rather long bristles and sometimes nods.

Secale cereale is the rye that is cultivated and from which rye bread is made.  But it also readily escapes from cultivation and can become weedy along roadsides and abandoned railroads - which is exactly what the W&OD trail is.  Given that, fifty years ago, this land belonged to the A. Smith Bowman distillery, which used rye (among other grains) to produce its Virginia Gentleman bourbon, it is entirely possibly that rye used to be cultivated in this particular patch and has persisted as a weed.

On the south side of Sunset Hills Road, between Isaac Newton Square and the pipeline, at the northwestern corner of the BAE Systems property, is this beautiful ornamental sweetgum (Liquidambar styraciflua), with its distinctive palmately lobed leaves.  Compare the Virginia Tech fact sheet.

This tree is now gloriously full with the characteristic gumball fruit.

Further west along the south side of Sunset Hills Road, the northern edge of the Plazamerica property is lined with ornamental sawtooth oaks (Quercus acutissima).  These oaks have long slender unlobed leaves like the willow oaks (Q. phellos) shown in this post, but are definitely a different species - note the bristly spines along the leaf edges and the exuberant fringe of scaly outgrowths covering the acorn cups.  Compare the Virginia Tech fact sheet.

Like the willow oak, the sawtooth oak belongs to the red oak group, which has acorns maturing in two years (unlike the white oak group, whose acorns mature in just one year).  The previous image showed some dark brown and mature acorns;  this picture, taken from the same tree, shows a green immature acorn that thus appears to be a year younger than the previously shown ones.

This tree, slightly further west than the previous one and more exposed to the sun, appears even further in its development - it has already dropped its mature acorns, leaving behind just the fringed cups.

Along the north side of the Plazamerica parking garage, fronting Sunset Hills Road, is this ornamental planting of oak-leaved hydrangea (Hydrangea quercifolia), which is acquiring a very attractive fall coloration.  Compare this data sheet from Missouri.

Let us now return to wildflowers!  Nestled among the mile-a-minute vines that infest the southeastern corner of the intersection of the W&OD bike path with Old Reston Avenue one can find this white five-petaled flower with a prominent cone of five anthers and distinctly lobed long leaves.

This appears to be Carolina horsenettle (Solanum carolinense), which, despite the name, is not actually a nettle, but rather a nightshade, closely related to eggplant and a bit more distantly to tomato and potato.  Compare this Illinois description and this Connecticut write-up.

Earlier this afternoon I had encountered another clump of Carolina horsenettles along the path leading from the parking lot of 1801 Robert Fulton Drive to the W&OD bike path.  These plants are obviously further along in their development;  they have finished flowering, and their berries (rather like small grape tomatoes, no?) are starting to ripen.  Warning - these berries are quite toxic.

And now for an old standard - yes, of course there are dandelions (Taraxacum spp., most likely T. officinale) in Reston.  This one is found in the lawn on the south side of the W&OD bike path just east of its intersection with Old Reston Avenue.

And where one sees a dandelion flower, one also soon sees a dandelion parachute ball ("Pusteblume", or "blow flower", in German), which contains the dandelion seeds ready for wind dispersal - just like the thistle seeds with which we started this afternoon.

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.

Afternoon of September 25, 2009

An overall view of the pignut hickory (Carya glabra) on Charter Oak Court described in more detail in this post.

Flowers and fruit on a crape myrtle (Lagerstroemia indica) on the northwest extension of Charter Oak Court.  According to the Digital Atlas of Virginia Flora, crape myrtles do not grow in the wild in Virginia, but they are extensively cultivated, and with their bright pink, red, purple, and white flowers dominate the summer suburban landscape. See this page for a suggestion of the humongous variety of crape myrtle cultivars offered in the horticultural trade - there is no hope for me determining what particular cultivar is planted here at Charter Oak Court.

A closer view of the flower of this crape myrtle.

A close-up view of the crape myrtle fruit.  We are toward the end of the long (2-3 months) flowering season for local crape myrtles, so most specimens now have more fruit than flowers on them.

One way crape myrtles can be instantly recognized even in the absence of flowers or fruit is by the presence of multiple stems with very smooth and shiny bark that exfoliates to produce this mottled appearance.  This particular specimen is on Jonathan Way just west of its intersection with North Shore Drive.

Yet another example of fall-time chlorophyll degradation in the distal areas of a leaf producing a green vein pattern.  These leaves, with their rounded lobes, clearly belong to a member of the white oak group (Quercus spp.), but not having seen an acorn, I cannot tell definitively whether this is a white oak (Quercus alba - see Virginia Tech fact sheet), an English oak (Quercus robur - see Virginia Tech fact sheet), or possibly another member of the group.  This specimen is growing wild in the hedgerow that separates Hidden Creek Country Club from North Shore Drive just south of its intersection with Jonathan Way.

A Virginia creeper (Parthenocissus quinquefolia) vine climbing a young tree trunk in the same hedgerow.  See the Virginia Tech fact sheet.  This vine is very common in the Charter Oak Court area, although along the section of the W&OD trail that I frequent the dominant vine is wild grape rather than Virginia creeper.  Both Virginia creeper and wild grape are native to the area, unlike kudzu, which I have not yet noticed here.

Close-up of a Virginia creeper leaf, showing it to be a palmately compound leaf composed of five serrated leaflets (hence the specific name quinquefolia, which is Latin for "five-leaved").  This readily distinguishes the Virginia creeper from wild grape, which has simple cordate (heart-shaped) leaves.

September 22, 2009

Right at the end of Charter Oak Court is this beautiful Kousa dogwood (Cornus kousa), which is native to eastern Asia.  Compare the description from Ohio State University and the Virginia Tech tree fact sheet.  All pictures in this post taken September 22, 2009, unless otherwise noted.

The most obvious aspect of the Kousa at this time of the year is its abundance of red compound berries.  Picture taken evening of September 21.

A closer look at one of the compound berries, which looks rather like a spiky red soccer ball.  Picture taken evening of September 21.

The berries are beginning to drop en masse, leading to quite a collection of fruit at the base of the tree.  Given that this is in a manicured lawn, there is no chance that any of these seeds will actually result in a new tree.  The Kousa is also not mentioned in either the Digital Atlas of Virginia Flora or the Checklist of Washington-Baltimore Area Flora, indicating that this tree is purely a planted ornamental and does not grow in the wild in our area.  Picture taken evening of September 23.

A bit further up the street/parking lot at Charter Oak Court is this pignut hickory (Carya glabra), also in full fruit.  Compare the Virginia Tech tree fact sheet.  Photo taken evening of September 21.

I found this very useful key to hickories from Vanderbilt University.  From this I was able to identify my hickory as a pignut.  As this picture shows, the leaves generally have 5 leaflets, which (in step 3 of the key) narrows it down to either pignut or shagbark hickory - and my specimen does not have a shaggy bark.

Moreover, the fruit have the unique pear shape of pignuts - see this gallery of hickory fruit and compare my specimen to those in the second row on the left.  Picture taken evening of September 21.

While quite a few of the fruit still remain on the tree, many nuts have also already fallen, littering the ground beneath the tree.  And as is evident from this shot, the local fauna (most likely squirrels) has been happily nibbling on them!

While the pignut at Charter Oak Court is a tended ornamental, I also found this wild pignut along the forested portion of the W&OD gravel path just north of Sunset Hills Road.  If you look closely at the high-resolution version of this picture, you can see at least three fruit still hanging on this tree.

A bit further north on the W&OD gravel path, near the top of the stony slope as you walk toward Michael Faraday Court, is this chestnut oak (Quercus prinus), with its characteristic crenately lobed (but untoothed) leaves and large acorns - see the Virginia Tech tree data sheet.  In this picture, which was taken with the camera pointing pretty much straight up, one acorn can still be seen hanging near the center.

The peak of the acorn drop for chestnut oaks was about two weeks ago, and the path underneath this particular oak is still completely littered with fruit.

This oak clearly reproduces in the wild, as shown by these two youngsters nearby (yes, these are rooted seedlings, not just fallen branches).

At the bottom of the large dip in the W&OD gravel path between Wiehle Avenue and Michael Faraday Court is this dense clump of late-flowering thoroughwort (Eupatorium serotinum).  Note the patches of summer grape (Vitis aestivalis), with their large heart-shaped leaves, lurking in the undergrowth.  See yesterday's post for more on these plants.

Here is a close-up of a flowering dogwood (Cornus florida) in the hedgerow that separates the W&OD gravel path from the Pizza Hut parking lot at Wiehle Avenue.  The buds that will open up to form next year's new leaves and flowers are already clearly visible.  Looking closely at the clusters of berries one can also see that not every flower has developed into a berry;  there are clusters of about 10 flowers each, with only three or four berries and the remaining flowers now undeveloped.

Back at Charter Oak Court, the color is definitely turning on the red maples (Acer rubrum).  It is my understanding that tree leaves contain a number of different pigments, including orange carotenoids  as well as the deep green chlorophyll.  Once chlorophyll has been deployed in a leaf, it dominates all the other pigments.  Chlorophyll has to be continually regenerated, and in the fall this process becomes less efficient and essentially restricted to the areas close to the leaf veins.  At the same time, production of red anthocyanins kicks in in the areas abandoned by chlorophyll (see this Wikipedia article for a more comprehensive explanation).  The spatial restriction of chlorophyll production can be clearly seen in these leaves, which are still green in the areas immediately adjacent to the leaf veins but russet in the outlying areas.

Leaves on another red maple at Charter Oak Court, once again showing the delicate green vein pattern that results from the gradual shutdown of chlorophyll renewal in these leaves.