Afternoon of October 22, 2009

Right next to the ornamental crabapple trees at the entrance to the parking lot at 1801 Robert Fulton Drive (shown in this posting) is this line of beautiful ornamental conifers - very much the traditional Tannenbaum of my childhood Christmases in Germany.

Given the four-square, rather stiff needles and the fact that the cones are hanging rather than standing erect on the branches, this is very clearly a spruce (Picea spp.) rather than a fir.  Because the branches do not droop, and the foliage (especially this year's new growth) is rather blue in color, I believe this is a blue spruce (Picea pungens).  See the Virginia Tech fact sheet.

The cones tend to be concentrated in the top portion of the tree and can be quite abundant, as seen in this specimen, which is located down the street from the one shown in the first photo and is lighted differently (the tree in the background is an oak).

The blue spruce can be compared with this spruce located in the Charter Oak townhouse development.  Note the drooping branchlets (also note the rather scraggly outline of the tree;  this and all other spruces in the townhouse development were recently pruned).  This is a Norway spruce (Picea abies).  Compare the Virginia Tech fact sheet.

A closer look at the Norway spruce, demonstrating that it is in fact a spruce (note the hanging rather than erect cones) and also suggesting that the cones are rather more elongated than the ones of the blue spruce.

Back on the W&OD bike path, clear evidence that botanical classification actually makes sense!  Thoroughworts (Eupatorium spp.) are members of the Asteraceae family, and thus, just like the thistles, dandelions, and goldenrods that are also classified in this family, the thoroughworts (like this one just south of the Dulles Toll Road bridge) develop white balls of tufted hair to carry off seeds in the wind once flowering has finished.

Another sight of beauty, this one on the north side of the W&OD gravel path at the top of the hill east of Michael Faraday Drive - a wild eastern redcedar (Juniperus virginiana), in full fruit.

Here is a closer look at some of the bluish-white berry-like cones, as well as the four-square branchlets covered in tightly-layered scale-like needles.

Just down the hill, in the northeastern corner of the intersection of the W&OD gravel path with Michael Faraday Drive, is this fascinating pine.  Note the very sharp spike at the end of each cone scale (the cone is quite prickly to the touch).  In this image, you can also see one or two seeds still clinging to the inside of some of the cone scales, especially in the upper right portion of the front cone - the scales themselves are not the trees progeny, but rather the pair of seeds sheltered by each scale.  Also note that the needles are relatively short and come in bundles of two.

On the tree you can find not only this year's new cones, but also quite ancient cones still attached to the tree - this is a pine that does not drop its cones.

In fact, some cones have remained attached for so long that all the scales have been stripped off, leaving just the bare core of the cone hanging on the branch!

Thus, when looking up into this tree, one is struck by the large number of dead cones still remaining.  Based on all of these criteria, this pine, according to Charles Williams's "The Pines of Virginia" (available here), is a Virginia pine or scrub pine (Pinus virginiana).  Also compare the Virginia Tech fact sheet.  This species is an early colonizer of abandoned fields;  thus, it makes sense to find it here along the abandoned railroad.

Compare the Virginia pine with the eastern white pine (Pinus strobus), shown here in a specimen from the north side of North Shore Drive near the Charter Oak townhouse development but very frequently encountered everywhere in Reston.  The eastern white pine has rather longer needles that are in bundles of five;  its cones are also larger, more elongated, and lacking a spine, and they drop after two years.  See the Virginia Tech fact sheet.

October 1, 2009 (continued)

There is a clump of thistles in the median between the W&OD bike path and the W&OD gravel path north of the Dulles Toll Road bridge.  These have been blooming for about a month now.  This picture was taken in the evening.

A closer view of the same plant, taken that morning.  Based on the criteria in Newcomb's Wildflower Guide, this can be identified as field thistle (Cirsium discolor).  See also this description from Illinois.  The leaves are whitish underneath, and the bracts (the green round golfball-like structure underneath the flowers) is not spiked as in bull thistle (C. vulgare).  Moreover, the flowers are not fragrant, and thus this is not pasture thistle (C. pumilum).  And the leaves are spiky and extend all the way up to the bracts, so this is not Canadian thistle (C. arvense).  Field thistle is native, unlike some of the other species.

I believe this unassuming little weed, on the north side of the W&OD bike path between American Dream Way and Isaac Newton Square, is common ragweed (Ambrosia artemisiifolia), the bane of allergy sufferers this time of the year.  Compare this Virginia Tech weed guide and this image page from Oregon.

Here is a closer view.  Although somewhat discolored by the effects of the camera flash, one can see both the somewhat bent spike of flowers as well as the characteristic deeply dissected leaf pointing down from the stem in the middle of the image.

I also had some success with distinguishing species in a genus.  As previously noted, most of the thoroughworts along the W&OD bike path are late-flowering thoroughworts (Eupatorium serotinum).  This image highlights the petiolated lanceolate leaves that are the distinguishing characteristic of this species.

But along the bike path south of the Dulles Toll Road I also found a couple of specimens of this smaller plant, with very narrow sessile leaves that do not increase in size as one goes down the stem.  This appears to be hyssop-leaved boneset (Eupatorium hyssopifolium).  Compare this page from the Connecticut Botanical Society.

And then there is this species, which occurs in a clump of winged sumac between the Access National Bank building at 1800 Robert Fulton Drive and the W&OD bike path just north of Sunrise Valley Drive.  This species has sessile leaves that are a bit blunter than those in E. serotinum and become more noticeably toothed as one goes down the stem.  Of the species listed in Newcomb's Wildflower Guide, this most closely answers to rough boneset (Eupatorium pilosum), though it might also be one of the other sessile-leaved thoroughworts, such as round-leaved boneset (Eupatorium rotundifolium).

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.

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.