Trees - April 23, 2010

While male strobili are already fully developed on Virginia pines (see this post from earlier in the week), they are not yet apparent in Eastern white pine (Pinus strobus).  Instead, all we have yet are these new shoots that will eventually develop either male strobili or female cones.

Note, though, how abundant the shoots are, at the end of each branch and branchlet - once the strobili develop, their pollen will be overpowering!  This specimen is in the parking lot of 1801 Robert Fulton Drive.

Meanwhile, this blue spruce (Picea pungens) near the entrance to 1801 Robert Fulton Drive (part of the group featured in this post from last fall) is in full "bloom".

Note the solitary male strobili hanging from the ends of the branches.  Also barely visible are several mature cones from last year that have already opened up and dropped their seed.

Here one can also see a new cone, still light brown and with its scales relatively closed.

Meanwhile, there is one large flowering tree that is now spectacularly in bloom - the black locust (Robinia pseudoacacia, see the Virginia Tech data sheet).

This specimen, which still has few leaves and thus is almost all white flower right now, is located on the north side of the W&OD gravel path just west of its intersection with the driveway for the Oak Hill Christian School.

This specimen is located along the southern border of the Sycamores apartment complex.  It has already leafed out more, showing the characteristic pinnately compound leaves of the black locust.  But this also shows a somewhat closer look at the drooping clusters of flowers - rather similar to the wisteria flowers, which is not surprising, given that both are members of the Fabaceae or pea family.

Near the black locust just shown is this black walnut (Juglans nigra), which is also in bloom, albeit not very spectacularly - note the hanging catkins of green male flowers in the center of the image.

A closer view of the black walnut catkins.  For a picture of black walnut in fruit last fall, see this post.

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.