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in February 2006

SEEDY SILHOUETTES

Just after dawn one day this week we grabbed our digital camera and 400mm telephoto lens to go out and shoot some seedy silhouettes at Hilton Pond Center. No, we weren't trying to capture the image of two passionate lovers outlined against a window shade; the kind of seediness we were looking for was high in the trees, where the angle of the morning sun backlit fruit still dangling from topmost branches. In midwinter--long after hardwoods drop their uniquely shaped leaves that help us know their species--it's still possible to identify many trees just by the shapes and silhouettes of their sometimes empty seed pods.

All text & photos © Hilton Pond Center

Perhaps the most distinctive and plentiful tree at Hilton Pond Center produces a plethora of prickly 1.5-inch brown balls that dangle from long, thread-like stems. If you've ever stepped barefoot on one of these little spheres, you'll recognize it as coming from Sweetgum, Liquidambar styraciflua (above). Sweetgum balls are the bane of the bird bander because each little prickle ends in a tiny hook that grabs tightly onto the mesh of mist nets used to capture birds. On a windy day, dozens of these balls can fall from the tree and tangle in a net--meaning the bander spends more time extricating Sweetgum fruit than catching birds.

Another tree species bears a spherical fruit similar in size to that of Sweetgum, but its texture is far different. The American Sycamore, Platanus occidentalis (above), has balls that are soft and almost downy. Most break into hundreds of little downy tufts that allow wind to disperse the attached seeds, so by this time of year it's not uncommon for a tree to have few intact seed balls. Several winters ago, as we stood beneath one of the Center's two sycamores, we were met by a continuous shower of fluffy seeds as a mixed flock of titmice, kinglets, and Yellow-rumped Warblers pecked through sycamore balls above.

We were particularly surprised this week to see fruit still hanging from topmost branches of a tree that usually drops its seeds--or has them plundered by arboreal mammals--by early or late fall. Right on the bank of Hilton Pond, a tall Common Persimmon, Diospyros virginiana (right), still held two of its bright orange fruits--each about two inches in diameter. From our ground-level vantage point it appeared the persimmons were whole and heavily wrinkled. We're willing to bet they've lost their notorious pucker power by now and are full of concentrated sugar that would be a terrific energy source for an animal aerobatic enough to harvest them.

Closer to ground level, several understory trees not far from the pond held dense clusters of seeds so dry we could hear them rustle against each other in the wind. These flat four-inch-long fruits were truly "pea pods," since they hung on a member of the Pea Family called Eastern Redbud, Cercis canadensis (below left). Since the seed clusters were not quite fully darkened silhouettes, we could see the pods had a series of bumps along their lengths--each bump being a raised section that covered the pea. To our knowledge, birds and mammals pay little attention to redbud seeds, although in closer view we often find tiny insect holes riddling the outsides of almost every pod.

A little further down the trail we found another tree bearing what looked like redbud pods--on steroids. Again we could see bumps where peas were hidden within, but in this case the pods were a foot long, thicker, and somewhat twisted. Along the main trunk were small clusters of sharp spines that deter herbivores--some of which undoubtedly would like to get at the contents the twisted pods of this Honeylocust, Gleditsia triacanthos (below). Although Honeylocust pods are tough and leathery, any organism industrious enough to peel open the pod--and that includes appreciative humans--will be rewarded by a sweet, gummy pulp that gives the tree its common name.

Among our tallest trees at Hilton Pond are those with straight, pale gray trunks that reach high into the canopy. On their top branches--up where the most sunlight is available--these trees erupt each spring with bright yellow blossoms shaped like tulips. In fact, these are called Tulip Trees, Liriodendron tulipifera, also known as Yellow Poplar. Curiously, the seed pod of the Tulip Tree is also tulip-shaped, as shown in the photo below. Seeds from these pods are long-gone, dispersed by wind or picked clean by birds from Carolina Chickadees to Downy Woodpeckers. At first glance one might not realize the Tulip Tree is actually in the Magnolia Family, but a close view of its flower anatomy next spring will reveal the relatedness.

One seedy silhouette we spotted grew on a shrub overhanging Hilton Pond itself. Although its fruit looked much like a pine cone, this was not an evergreen but a deciduous woody plant called Hazel Alder, Alnus serrulata. A water-loving member of the Birch Family, these alders--as early as February--will be producing male catkins bearing copious amounts of pollen that, in turn, fertilizes female flowers that give rise to the tiny half-inch cones (below right). In 1982, when we first moved to the property that is now Hilton Pond Center, few alders grew around the pond; however, within five years after we abandoned the previous owners' clear-cutting regimen, these water-loving plants had grown to form a nearly solid wall of vegetation around the bank. Alas, when an extended drought began in the late 1990's, the waters of Hilton Pond receded, the alders dried out and died, and now we have very few left of cone-producing size. With that major drought behind us pond water levels are up again, so we're hopeful the few remaining alder cones will produce enough seed to repopulate the banks.

Growing among the alders was a spindly 15-foot-tall shrub with drooping five-inch clusters of dark red quarter-inch berries. In some clusters, the berries had fallen, leaving behind a dense fibrous structure. Even in silhouette (below), this plant was recognizable as one of the sumacs--in this case Smooth or Common Sumac, Rhus glabra. This species--along with Staghorn Sumac, R. typhina, and Dwarf or Winged Sumac, R. copallina--yields berries that can be boiled down and steeped into a delicious lemonade-like beverage. Because this drink is so refreshing to our palate, we've always been surprised all three sumacs tend to hold their berries most of the winter; it's a mystery to us why birds or mammals such as chipmunks don't glean and devour sumac fruit as soon as it ripens.

Our last seedy silhouette this week was one recognizable even to many folks who aren't nature enthusiasts, if only because the tree is common--and welcome--in yards throughout the central and southeastern U.S. We refer here to the Pecan, Carya illinoinensis (below), whose tasty nut is collected by homeowners speedy enough to beat local squirrels to the tree's fall bounty. Although we have some massive old Pecan trees at Hilton Pond Center, we almost never get to taste their nuts--and not just because of competition from our local "bushy-tailed tree rats." We've never had a big yield of Pecan nuts--probably because we don't fertilize our trees to increase productivity--but some nuts ARE produced each year, as indicated by numerous open husks still on the trees in winter (below left). As a pecan ripens, the husk surrounding it opens to release the fruit, but we're guessing squirrels grab most ripened nuts before they even hit the ground. A goodly number of our pecans instead fall victim to nut-boring weevils and other insects. Those "nutivores" produce larvae that live and grow--and eat--within the pecan's protective shell, eventually consuming all the nutmeat in their bedroom/pantry. When this happens, a pecan may still reach full size, but apparently some mechanism keeps the husk from opening, as shown in the photo below right. Whether the husk is open or shut, however, the tree in both photos is still recognizable as a Pecan.

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All text & photos © Hilton Pond Center

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Be sure to scroll down for an account of all birds banded or recaptured during the week, plus other nature notes of interest.

"This Week at Hilton Pond" is written & photographed
by Bill Hilton Jr., executive director of
Hilton Pond Center for Piedmont Natural History.

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