Afternoon of September 27, 2009

The following pictures were taken near the eastern end of the hedgerow on the northern side of the Charter Oak apartment complex that separates the complex from the Hidden Creek Country Club golf course to the north.

Most of the trees in this hedgerow are tulip trees, also known as yellow poplars or tulip poplars (Liriodendron tulipifera).  They are instantly recognizable by their unique large four-lobed leaves.  Compare the Virginia Tech fact sheet.  The bud-like structure in the center of this picture is the fruit of this tree, consisting of numerous samaras that will apparently float off in the next month or so.

In the understory there is this isolated occurrence of tree of heaven (Ailanthus altissima).  Compare the Virginia Tech fact sheet.  This is a highly invasive weed species;  see this National Park Service fact sheet for details.

The large brown structures are the remnants of its seed pods;  from their size and number you can tell that this tree is a prolific seed producer, which is what makes it such a success as a weed.

Tree of heaven has large pinnately compound leaves, much like walnuts and sumacs.  The way you can tell a tree of heaven leaf is that each leaflet is smooth-edged except for a distinct notch near the base on both sides of the leaflet.  Walnuts and sumacs, by contrast, have serrate (finely toothed) leaflets.

Just beginning to bloom at ground level is this small-flowered white-rayed aster (Symphyotrichum spp.).  There are a large number of asters, which are apparently difficult to distinguish.  Cross-referencing the small-flowered white-rayed asters listed in Newcomb's Wildflower Guide to those listed as growing wild in Fairfax County in the Digital Atlas of Virginia Flora, it appears this could be either calico aster (Symphyotrichum lateriflorum - see this description from the Connecticut Botanical Society) or frost aster (Symphyotrichum pilosum - see this description from the Connecticut Botanical Society).

The hedgerow also features several black walnuts (Juglans nigra), which are now magnificently in fruit;  the green husks, which contain the walnut, are about 2-3 inches across.  Compare the Virginia Tech fact sheet.  Note that this is black walnut, and not butternut (J. cinerea), as the fruit are round rather than lemon-shaped.  Black walnut is found not infrequently in the wild woods of Reston.

 

Virginia creeper (Parthenocissus quinquefolia), with its distinctive five-part palmately compound leaf, is the dominant vine in this hedgerow.  Here it can be seen as both ground cover as well as climbing the trunk of a tulip tree.  This is the view from my living room window.

The dominant maple in both the hedgerow and the landscaped portions of the Charter Oak apartment complex is the red maple (Acer rubrum).  But the hedgerow also contains this sugar maple (Acer saccharum), with the leave shape familiar to us from the Canadian flag.  Compare the Virginia Tech fact sheet.

Toward the very eastern end of the hedgerow is yet another species of maple, the silver maple (Acer saccharinum), whose large leaf is deeply dissected.  Compare the Virginia Tech fact sheet.  The only other silver maple I have noticed so far in Reston is in the Charter Oak Townhomes complex.  In this image (which was taken pointing straight up), also note the pinnately compound leaves of a black walnut higher up in the canopy.

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.

Clarification on grape nomenclature

It appears I was too hasty in this post in identifying the wild grape as summer grape (Vitis aestivalis).  My grape does match the description in this Virginia Tech data sheet.  However, as this website on Northern Virginia ecology points out, "there are several species of Wild Grape in Virginia, most of which are very similar and difficult to tell apart."  The Digital Atlas of Virginia Flora lists five Vitis species as occurring in Fairfax County:  V. aestivalis, V. labrusca, V. riparia, V. rupestris, and V. vulpina.  I have not yet found a key that distinguishes these five species, so I cannot really identify my grape closer than the generic Vitis spp.

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.