Morning of May 7, 2010

White clover (Trifolium repens, see this Missouri description and this Virginia Tech weed guide) is in bloom across Reston now.  This particular clump is in front of the Exxon station at the intersection of Wiehle Avenue and Isaac Newton Square.

Also very prominent now alongside paths and in unmown areas is this relatively tall grass with distinctive thick seedheads that form a triangular plane.  This particular sample is on the east side of Wiehle Avenue just north of its intersection with the W&OD bike path.  Also highlighted by the low sun in this image are some smaller grasses of a different species that I have not yet been able to identify, but which may be a form of Poa spp.

Here is another specimen from further south along the W&OD bike path.  It is a bit farther along in its development, with anthers now protruding from the seedheads.  I believe this grass is orchard grass (Dactylis glomerata);  compare this Missouri description and this Wikipedia article.

On either side of the W&OD bike path, as here just east of Michael Faraday Drive, large thickets of blackberries (Rubus spp.) are now in bloom.

Not all flowers on a cane bloom at the same time (some of the flowers in this image have already lost their petals);  if they did, this would be even more spectacular.  Note that complete flowers have five relatively large elongated petals, and the leaves generally are composed of three leaflets.  This may be southern or sawtooth blackberry (R. argutus, see this Virginia Tech fact sheet, this Duke description, and this Missouri description).

At the same time, there is another thicket-forming shrub that is at the peak of bloom, as here on the north side of the W&OD bike path just east of Michael Faraday Drive.  This is the multiflora rose (Rosa multiflora), a highly invasive species (see this Virginia Tech fact sheet and this National Park Service indictment).  For an image from last October of the red berries born by the multiflora rose, see this post.

A close-up of the multiflora rose.  Unlike with the blackberries, all of the flowers on the rose are blooming at the same time.  Also, the white petals are a bit wider and less elongated, and the flowers have prominent clusters of yellow stamens at their center, unlike the blackberry flowers.  Finally, the leaves have 7 to 9 rather smaller leaflets.  Thus, even though both the multiflora rose and the blackberry belong to the Rosaceae family (along with cherries, pears and apples), they are easily distinguishable.

This grape vine (Vitis spp.), on the west side of the W&OD bike path just south of Sunset Hills Road, is now also in bloom, albeit very inconspicuously.

Evening of April 12, 2010 (cont.)

Another tree that is in bloom now is the crabapple (Malus spp., potentially Malus floribunda, the Japanese flowering crabapple).  This specimen is located at the entrance to the parking lot of 1801 Robert Fulton Dr and was previously featured in this post from last fall.

A close-up of some of the flowers on this crabapple - the family resemblance to cherries, plums, and pears is quite evident (all are members of the rose family).

On the north side of the W&OD bike path, between Wiehle Ave and Isaac Newton Square, is this wild specimen that I believe is also a crabapple.  Being in Reston's weedy wilds rather than on a manicured corporate campus, it is being strangled by grape vines (Vitis spp.);  the emerging grape leaves can be seen above the sprig of blossoms.

Another tree that is still spectacularly in flower is the Kwanzan cherry (Prunus serrulata, see the Virginia Tech data sheet), which is the last of the wide-spread Japanese cherries in our area to bloom (the native black cherry, P. serotina, will not bloom  for another month or so).  This specimen is on the edge of the Cardinal Bank parking lot facing the W&OD bike trail between Sunset Hills Drive and Michael Faraday Drive.

A closer look at the frilly double flower of the Kwanzan cherry.

Ah, what a beauty!

And of course the other charismatic flowering tree of this time of the year is the flowering dogwood (Cornus florida, see the Virginia Tech fact sheet), which together with the eastern redbud dominates the understory.  This particular specimen is on the north side of the W&OD bike path just west of Michael Faraday Drive.

A closer look at the characteristic dogwood flower in full development, with the cruciform sepals.  For a look at how the dogwood looks in the fall, see this post.

But the most prolifically blooming plant right now may well be the autumn olive (Elaeagnus umbellata, see the Virginia Tech fact sheet), which is highly invasive and festers all up and down the W&OD bike path (this particular specimen is seen from the Cardinal Bank parking lot).

The branches and shoots of this shrub are now all lined with very fragrant flowers whose heavy, sticky smell overpowers the earlier sweeter scent of the pears and cherries.  This specimen is just south of the Dulles Toll Road bridge over the W&OD bike path.

A closer look at the autumn-olives abundant flowers.  For a look at the equally abundant berry-like fruit generated from these flowers in the fall, see this post.

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.

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.