Connections: The Pawpaw Tree and the Zebra Swallowtail Butterfly

Asimina triloba and Eurytides marcellus

By Laura Seale

Editors: Devin Floyd, Clyde Kessler and Scott Jackson-Ricketts

A pair of survivors
The Zebra Swallowtail butterfly and the Common Pawpaw tree have been through a lot together. If you see one of these distinctive long-tailed butterflies glide past, it's likely there's a pawpaw patch nearby. The Zebra Swallowtail, Eurytides marcellus, is the only species of the genus Eurytides (the kite swallowtails) that makes its home in the temperate zones of North America. Other species from this genus live in subtropical zones. The sole source of food for the Zebra Swallowtail's caterpillars is the foliage, particularly the young leaves, of trees in the genus Asimina, the pawpaws. It happens that the Common Pawpaw, Asimina triloba, from the same family (Annonaceae) as the tropical custard apple and cherimoya, is also the only of the Asimina genus that is able to grow in this region of temperate North America, suggesting that the Zebra Swallowtails and the pawpaws have been co-evolving here since this region was very different than it is today.

A first good look
The first time I saw a Zebra Swallowtail, it was clinging with wings broadly spread, to a piece of tall grass at the edge of a cluster of pawpaw trees. Wind gusts from an approaching storm were keeping it grounded, which gave me ample time to admire and study its bold coloring. Its wings are more triangular in shape (with a span ranging from 2.5 to 4 inches) and its “tails” are longer and more slender than those of our other native swallowtails. Along with the zebra-stripes of black and greenish-white, the Zebra Swallowtail has two blue spots at the base of the upper surface of the hindwing, another bright red spot close to the body, and a red median stripe on the underside of the hindwing. The summer zebras are darker, with thicker black wing-stripes, and have longer tails than the ones that hatch early in spring.

Caterpillars' diet for self-defense
The Zebra Swallowtail female chooses young terminal leaves of the pawpaw on which to lay her eggs. The eggs are laid singly, one per leaf, because if the caterpillars encounter each other, they become cannibalistic. Those young paw paw leaves and their stem bark are especially rich in acetogenins, chemicals that make the foliage unpalatable to browsers, like deer and rabbits, and the leaf-munching caterpillars distasteful to potential predators. The Zebra Swallowtail mamas might get a little help from a pyralid moth called the Asimina webworm moth, Omphalocera munroei, that eats older leaves of the pawpaw to encourage growth of new acetogenin-rich terminal leaves.

Life as a zebra swallowtail
The Zebra Swallowtail larvae are hairless and appear somewhat humpbacked. When young, the caterpillar is dark with with many narrow transverse bands of black, yellow, and white. When older, they still have the stripey rings, but are greener, and often have one thicker black band across the top of the first abdominal segment. Like some other swallowtail caterpillars, the Zebra Swallowtail caterpillar can fend off predators by pushing out its osmeterium, which is a yellow, forked organ that emits foul-smelling odors. These odors are synthesized from essential oils, called terpenes, in the host plant. When ready, the caterpillars pupate under pawpaw leaves. Their pupae are green or brown and patterned to look like a curled leaf. After hatching, the females stay near the pawpaw patch, while the males can be seen patrolling for females, or puddling, sipping mineral rich water from moist soils. The adults nectar at a variety of flowers, including common milkweed, dogbane, redbud, and blackberry. It is notable that this butterfly only occasionally strays to elevations above 3000 ft. since it generally stays in the lower elevations where the pawpaws are.

Pawpaws' ploy for pollination
Of no interest to the Zebra Swallowtail butterfly are the pawpaw's flowers, as the butterflies do not pollinate the flowers or nectar on them. In fact, there is relatively sparse pollination of the early spring flowers, resulting in few fruits compared with the number of blooms. The flowers of Asimina triloba are reddish-brown, looking and smelling like rotting meat to attract carrion flies and beetles (and occasional Polygonia species butterflies). As pawpaws are not self-fertilizing, they require pollinators to travel from patch to patch. Local flies and beetles are not especially effective with this pollination, begging the question: “Was there once a more efficient pollinator, perhaps gone the way of the long-extinct mega-herbivores that roamed this continent in the past?”

Seeds can't move themselves
In addition to lacking ideal pollinators, pawpaws also lack an ideal method of seed dispersal. I have personally slipped (a la banana peels) down a hillside slick with fallen pawpaws, coating my seat with fermented pulp, wondering as I fell why there were so many of these sweet fruits rotting underfoot. It's possibly because our native Common Pawpaw is an anachronism, missing its original seed dispersing agents. The pawpaws may have evolved with the elephant-like mastodon and other extinct mega-fauna like the American camel and the giant ground sloth. The seeds are too large to be ingested, transported, and dropped in the dung of even our largest existing native herbivores, with the possible exception of the black bear. Deer show little interest in the leaves or the fruit, probably due to the plant’s chemical defenses. Since the extinction of mega-fauna, humans have likely been responsible for most of the redistribution of pawpaw seeds.

Patches of clones

One reason why pawpaws have continued to exist in this region, despite the spotty pollination and the lack of wide seed dispersal is their habit of cloning. The long-lived roots send up genetically identical suckers. The young trees are able to grow in the shade of the older ones, which eventually form the clonal “pawpaw patch.” Though the individual trees themselves tend to be short-lived, no one knows how old the root systems in pawpaw patches can get.
"Connections". Can you think of ways that this sketch says, "pawpaw"? The sketch includes a variety of indirect references to the pawpaw tree. (See bottom of article for some answers). Print the image above as a coloring sheet (PDF)

Native food staple

The first historical mention of pawpaws was in a 1541 report from an expedition of Spanish explorer, Hernando de Soto. His party observed Native Americans cultivating and eating pawpaws. John Lawson, an English explorer, wrote about encountering Native Americans using pawpaws in his 1709 book,
A New Voyage to Carolina: “ The Papau is not a large Tree. I think, I never saw one a Foot through; but has the broadest Leaf of any Tree in the Woods, and bears an Apple about the Bigness of a Hen's Egg, yellow, soft, and as sweet, as any thing can well be. They make rare Puddings of this Fruit.”

Small but chemically significant
Common Pawpaw trees often grow in the understory of a forest. They don't get very tall, their maximum height being about 40 feet. The bark is brown and relatively smooth, though covered with wart-like pores. The leaves are large, 5-11 inches long, and obovate in shape, which means they broaden towards the leaf tip. If you crush a leaf with your fingers, you'll find that it has an unpleasant smell (unless you like the smell of fresh asphalt). Chemical compounds from the pawpaw stem bark and ground seeds have been used medicinally for their insecticidal and anti-parasitic properties, and their annonaceous acetogenins are now being studied as a potential cancer treatment, as they seem to inhibit tumor cell growth.

A local fruit worth trying
Pawpaw fruits start out green, then ripen through yellow to a purplish-brown. They often grow in small clusters, which have a way of hiding under the large leaves. The fruits of the Pawpaw have custardy pulp, and 10-14 tough seeds that look like big brown beans. Some liken their flavor to banana or pineapple, though the ones I have eaten taste like a very mild soft mango. Around Central Virginia, the fruits ripen in mid to late August. People make them into puddings and pies. I have eaten pawpaws fresh, in ice cream, and in paw paw bread (recipe similar to banana bread). Cooking with them is more labor-intensive than using thick-skinned bananas or fruit with a convenient single pit, but since they are the closest thing to a locally grown, tropical-tasting fruit, and since I have a free source of pawpaws, they are worth the effort. Considered delectable by many, pawpaw fruits are not widely distributed in supermarkets due to the easily bruised flesh and short shelf-life of the ripe fruit. Large-scale commercial pawpaw cultivation schemes have not been successful so far, due to the difficulties with pollination. Maybe someday pawpaws will be available in grocery stores of every region, but for now they're an exclusive treat for to those lucky enough to find a pawpaw patch. Just follow the Zebra Swallowtails.



Some answers to the sketch "connections" question above:
  • The human in the sketch is a Native American child. Native Americans utilized the pawpaw tree as a food source.
  • The plant in the middle ground is Apocynum cannabinum (Indian hemp, hemp dogbane) and was a primary fiber material. It was used to make string, rope, bags, sacks, and many other things. It is not out of the question that a collection bag or basket constructed of Apocynum cannabinum fiber would have been used to collect pawpaw fruit.
  • The zebra swallowtail frequents Apocynum cannabinum for its nectar.
  • The pawpaw tree is the zebra swallowtail's only host plant. It's caterpillar can't survive without it.
  • Those are wild turkey feathers in her hair, and the wild turkey loves pawpaws fruit.
  • Her necklace might contain pawpaw seed beads. The seeds are beautiful and hard.
The sketch illustrates, in a simplifed way, the very circular nature of connections between things. A pawpaw tree can be communicated without actually showing it.

Trees in the Ground!


Grayson Highlands School is positioned in a broad valley near Troutdale, Virginia. Opening this fall, this K-12 school consolidated Bridle Creek and Mount Rogers schools. In time, it will serve a larger student body, but during the transition, many kids in the neighborhood continue to attend school in Independence. Last winter, John Alexander, principal, several community members and Blue Ridge Discovery Center volunteers met to discuss broad ideas based upon outdoor classroom activities. The grounds on campus are essentially a blank slate, inspiring us to approach the possibilities with creativity and student owned ideas.

Earlier this fall, Clyde Kessler, BRDC Board Member, initiated a tree planting program at the new school by making a donation towards a tree or two. This donation grew as others heard about the program, with Carol Broderson and Blue Ridge Birders Club chipping in. After doing some research and consulting a variety of tree experts, including David Richert with Virginia’s Department of Forestry, we settled on a list of species that would do well on this windswept sandy spot.

Taking this list with me to Jones Nursery, Woodlawn, Va., on Tuesday, November 23rd, I met with Charlie Jones and Roger Hollinger, who helped me pick out and load up what $250.00 could buy. Charlie took an interest in our project, and not only helped me find the healthiest trees, but donated two large sugar maples to the cause. Charlie and Robert were incredibly helpful, including loading me up with stakes and pipe to help protect the trees from wind and deer.

The tree list is as follows:

I then headed west to the school, where Rebecca Absher, our point person and science teacher, met me, and with several older students we began to dig the holes and plant trees. There was not enough time left in the day to plant more than three, and with the Thanksgiving Holiday upon us, we were forced to wait until the following week to complete the planting. I left the school after securing a promise that all of the trees would be properly watered. Subsequent rains through the weekend further insured that the trees would be fine.

Realizing the magnitude of the job ahead, meaning digging six large holes in very hard ground, I reached out to our local BRDC volunteer pool and received the promise of help from Carol Broderson, Niki Weir, William Roberts and Larry Paluzzi. We all met, (and just in the nick of weather time), at the school on Thursday, December 2nd. Devin Floyd joined us for an hour, on his way to Independence for another BRDC program.
Again, with a great deal of help from the kids, we succeeded in planting the rest of the trees, including roping them off and attaching the protective tubing. It was plenty cold and breezy, as can be seen in the pictures, but spirits remained high. Planting a tree is a commitment to and an association with the future. We pointed out to the kids that as they grow, so will the trees, and it will be fun to look back on this day while sitting under the shade of a spreading oak or maple.

This small but significant first step on the school grounds merely sets the stage for future activities. Among our ideas is to create a tree nursery on site, a protected space for planting seedlings and even seeds for later transplanting. From here on out, the kids are going to study the grounds with trail and garden in mind. The next step is to have the kids create a map of the campus, and then begin the process of thinking about where they would like to plant a grove, what they might place along the edges, as well as how best to utilize the resource of a small branch and wet zone on one corner of the property.

By Scott Jackson-Ricketts
photos © Scott Jackson-Ricketts and Devin Floyd

Exploring Blue Ridge Flora and Geology

On November 13, the Rivanna Chapter of Virginia Master Naturalists and friends from the Native Plant Society went on a stroll to learn more about the flora and geology of the Blue Ridge Mountains.

The crew of nearly forty people explored the Jack Albright Trail (opened 2005) and the old Appalachian Trail near Humpback Rocks. Chip Morgan was the guide, and he was assisted by Russell Fitzgerald who shared the history of the local people from the long association his family has with this area.

During the hike the large group stopped frequently. The Catoctin formation meta-basalts are well known for the floral diversity they can support. The landscape in this area is also traced with a variety of features that echo human activity. This was a complex landscape, one that was impossible to soak up in a single day!

Below you will find a list of trees, ferns, a geologic description (map showing paleogeography included), and a link to a prior blog story exploring the geology and flora of Humpback rocks.

List of trees and shrubs observed:

1. Northern Red Oak, Quercus rubra

2. Chestnut Oak, Quercus prinus

3. Black Oak, Quercus velutina

4. White Oak, Quercus alba

5. Pignut Hickory, Carya glabra

6. Mockernut Hickory, Carya alba

7. Yellow-Poplar, Liriodendron tulipifera

8. White Ash, Fraxinus americanus

9. Black Birch, Betula lenta

10. American Linden, Tilia americana

11. Black Locust, Robinia pseudoacacia

12. Red Maple, Acer rubrum

13. Striped Maple, Acer pensylvanicum

14. Norway Maple, Acer platanoides

15. Black Cherry, Prunus serotina

16. Persimmon, Diospyros virginiana

17. Paulownia, Paulownia tomentosa

18. Spicebush, Lindera benzoin

19. Pinxterflower, Rhododendron periclymenoides

20. Alternate-leaf dogwood, Cornus alternifolia

21. Mapleleaf viburnum, Viburnum acerifolium

22. Hop Hornbeam, Ostrya virginiana

23. Sassafras, Sassafras albidum

24. Witch-hazel, Hamamelis virginiana

25. Serviceberry, Amelanchier sp.

26. American Dogwood, Cornus florida

27. Hawthorn, Crataegus sp.

28. Black Haw, Viburnum prunifolium

29. American Chestnut, Castanea dentata

List of Ferns Observed

  1. Rockcap fern, Polypodium virginianum complex
  2. Christmas fern, Polystichum acrostichoides
  3. Marginal wood fern, Dryopteris marginalis
  4. Ebony spleenwort,Asplenium platyneuron
  5. Upland brittle bladderfern, Cystopteris tenuis (leaves not present, but habitat pointed out)

Geologic description (adapted from USGS description; source below*):

Rock Type: Metabasalt (Catoctin Formation)

Age: Proterozoic Z-Cambrian

Paleo-geographical map (Notice the character and location of the terrain during the time of these basalt flows!!) http://jan.ucc.nau.edu/~rcb7/namPC550.jpg

Description: grayish-green to dark-yellowish-green, fine-grained, schistose chlorite- and actinolite-bearing metabasalt, commonly associated with epidosite segregations.

Minerals: chlorite + actinolite + albite + epidote + titanite +/- quartz + magnetite. Relict clinopyroxene is common; biotite porphyroblasts occur locally in southeastern outcrop belts.

Geophysical signature: The Catoctin as a whole has a strong positive magnetic signature. However, between Warrenton and Culpeper the lowest part of the Catoctin, which consists of low-titanium metabasalt and low-titanium metabasalt breccia, is non-magnetic, and displays a strong negative anomaly. Metabasalt is by far the most widespread unit comprising 3000 feet or more of section

Primary volcanic features : vesicles and amygdules, sedimentary dikes, flow-top breccia, and columnar joints, relict pillow structures.

*Source: http://tin.er.usgs.gov/geology/state/sgmc-unit.php?unit=VACAZc;0


Prior posting that may be of interest:

Lava Reaching Skyward

Remarkable Trees of Virginia Hike ….the Shenandoah National Park

Tulip Poplars of Pocosin Hollow

It is just one of those timeless places, achieved through a combination of old growth forest and the remains of early settlers' hard lives there. Exploration off trail in the hollow bottom and on the flat ridges will be well rewarded.

This is a partial description of a 5 hour day hike with an elevation change of close to 1000’ and starting on skyline drive at the PATC Pocosin Cabin Parking (Milepost 59.8) that a group of 14 Virginia Master Naturalists did on October 16, 2010. After following the old fire road past the cabin, and taking a short detour to the old mission ruins on the right a little over a mile in, continue down the road and take the Pocosin Hollow trail down to the left in less than ½ of a mile more. There is a signpost there on a concrete marker.

The trail is wide , in great shape and easy to follow downhill for another mile to a stream crossing…after crossing you will look for an old road going upstream, and 2 old wooden gate posts in 300 yards will confirm you are on the right track. The old road has several dead falls , branches lying along it you will need to step over , but is generally easy to follow for about 600 yards to the immense tulip poplar in the photo.

If you continue up the stream valley , you will pass under an unbroken grove of poplars with little understory , for about ½ mile. Small native chestnuts and cucumber magnolias are also found here. Further off trail exploration will show evidence of early settlement here.

The return trip can be done in about 1 1/2 hours, as the trail is well graded and switchbacks often…occasional views across the upper hollow, to Lewis mountain are found in the middle half…The October 16 trip actually left the Pocosin Hollow trail very soon after joining it, and came down the stream valley on the left side of the stream to the poplars, adding additional time. One can truly appreciate the wildness of Shenandoah National park this way …
In the book, Remarkable Trees of Virginia, which spawned this hike, the trees are referred to as the "largest trees in aggregation" in the National Park that naturalist Mo Stevens has seen in more than 35 years of walking there. The trees seem to be about 120 feet tall, and the rich soil along the hollow bottom support this kind of growth, as evident in the oaks and mountain laurels as well. For some reason or another, this grove of trees was spared the axe in early settlement of what is now the park...The poplar in the photo easily exceeds the height of the others! Great hike for those who love trees …

By John Holden,
Virginia Master Naturalist and Blue Ridge Mountain Sports Manager
Photographs © John Holden

For more information about the Yellow-poplar tree visit:
For more information about the Virginia Master Naturalists organization, visit:


Exploring Grindstone

This forest chews lava, and exhales the whispers of glaciers...

Sipping from rock once fuming and flowing
Drawing from deep water pebble-pimpled silt,
Splitting muck-mired cobbles of glacial mowings
Benefacting cycles of rise and wilt...

This forest chews lava, and exhales the whispers of glaciers...
-D. Floyd

On Sunday the 12th, a mother, a father, and a son explored the forest at Grindstone Campground on the north side of Mount Rogers. We were there to 'see what we could see'. Our walk took us around the short Grindstone loop trail, the 'Whispering Waters nature trail'. As has been experienced in the past, the beauty is blinding and the diversity overwhelming. One passes through at least two distinct forest types and transitions from glacial lake deposits to lava flow remains.
The forest along the upper portion of the trail is truly unique, as it is dominated by linden, ash, and cucumber magnolia. The great number of seeps along the trail provide for excellent exploration and the make-up of the forest shifts around every corner!

Here's a small bit of what we saw:

Rock type #1, near the beginning of the trail, is :

Konnarock Formation; Maroon diamictite, rhythmite, and arkose. These are rocks that were deposited in habitats that included deep icy lakes and glacial activity. They are the silicified (fancy word for 'turned into rock') remains of muds, silts, pebbles and cobbles carried by glaciers. Interestingly, the stones seen in the silicified mud were dropped into that muck and consist of materials from formations nearby...ryholites, greenstones, and granites. This makes sense because the glaciers would have been eroding these materials from the land during that time...and, it was a landscape devoid of plants and animals!...mountains and valleys of pure rock, silt, and sand!

Rock type #2, as one heads up the trail the rocks change to:

Mount Rogers Formation; Phenocryst-poor rhyolite. These rocks are a dark purple, and are the results of lava flows! Mount Rogers, White Top, and Pond Mtn. (NC) form the core of what was a massive and explosive volcanic complex. These once towering volcanoes have seen a lot of erosion, and have even found themselves buried beneath miles of sediment at different points in the geologic past. But today, we are afforded a view of these ancient volcanoes. It is worth noting here that this rock known as "Rhyolite" is high in silica, and breaks kind of like glass (chonchoidal fracture). This made it a choice material for use in making spears, knives, and other tools during prehistoric times. Somewhere on these mountains hides ancient quarries used by Native Americans!
Primary source: Virginia Division of Mineral Resources, 1993, Geologic Map of Virginia.

Trees and shrubs:

chestnut oak, Quercus prinus
northern red oak, Quercus rubra
red maple, Acer rubrum
sugar maple, Acer saccharum
striped maple, Acer pensylvanicum
black cherry, Prunus serotina
yellow birch, Betula alleghaniensis
black birch, Betula lenta
American beech, Fagus grandifolia
Fraser magnolia, Magnolia fraseri
cucumber magnolia, Magnolia acuminata
witchhazel, Hamamelis virginiana
viburnum sp.
yellow buckeye, Aesculus flava
green ash, Fraxinus pennsylvanica
white ash, Fraxinus americana
American linden, Tilia americana
rhododendron sp.
yellow poplar, Liriodendron tulipifera
eastern hemlock, Tsuga canadensis
...and, maybe Carolina Hemlock, Tsuga caroliniana (need to revisit the site to verify)

Scientific name reference: www.plants.usda.gov

Two unidentified species of the Lycopodiaceae family.

Smaller plants:

ramps, Allium tricoccum
white baneberry, Actaea pachypoda
Solomon's seal, Polygonatum sp.
false Solomon's seal, Smilacina racemosa
Pipsissewa, Chimaphila maculata
Dutchmans pipe, Aristolochia macrophylla
ground cedar, Lycopodium sp.
clubmoss, Huperzia sp.
partridge Berry, Mitchella repens
white snakeroot, Ageratina altissima
black cohosh, Actaea racemosa (syn. Cimicifuga r.)
blue cohosh, Caulophyllum thalictroides
yellow mandarin, Disporum lanuginosum
jack in the pulpit, Arisaema triphyllum
Curtis's goldenrod, Solidago curtisii
**Two aster species remain unidentified, see images below.
**Two Lycopodiaceae species remain unidentified. see image above.

My identification sources:
Newcomb's Wildflower Guide, by Lawrence Newcomb

On the way home we could not resist stopping to take in a phenomenal meadow. Willows, hawthorns, alders, cinnamon ferns, golden rods, ironweeds, ladies' tresses and butterflies galore. This little boggy area is very close to Grindstone Campground and can be thoroughly enjoyed from the road. I suspect there are many locations in the Grayson highlands area that are similar to this one, as it is maintained as pasture.

Never ending discovery

Spicebush Swallowtail Caterpillar (pre-pupal coloration)
©Scott Jackson-Ricketts

After the Radford BRDC Board Meeting, Devin and I regrouped at my place in Grayson County. After some review of the day’s events, we took a short but productive walk between my house and shop, mostly along the driveway. A few days prior, while being the busy guy in my shop, I found a caterpillar climbing up one of my recently painted shelving boards, which turned out to be a late instar spice bush larva. The information we sought while trying to understand the unique color of this caterpillar confirmed that just before it pupates, its color changes from green to orange, yellow or some combination therein. I would call what these pictures convey, peach.

Going on that inspiration, we headed straight to the spice bush known to me near my shop. Devin and I spent some time trying to find either another caterpillar or a pupated form, which Devin might have discovered five feet from the bush on the downside of a leaning black cherry tree. His photos reveal that what he found is indeed a swallow-tail, but not definitively spice bush. Another contender could be eastern tiger swallow-tail.

After that relative success, and while heading back to the house, we took our time observing activity among the wingstems and other late summer wildflower blooms, just paying that kind of attention we both share. Near the fork in our driveway that becomes the circle serving two homes, we found an unfamiliar wood shrub with both catkins and fruit present on the branches. Neither of us had ever seen this small tree before, and immediately grabbed a fruit sample, both acquiring simultaneously the precious sharp stabs from the needle like covering, reminding us of cacti.

Back at the house Devin immediately went for the field guides and soon reported that the woody shrub was a beaked hazelnut. While I cooked up some mush, he spent some time looking through my dissecting microscope, which showed us that the needles were almost glass like in appearance, with the light showing through. Very delicate and sharp, as we already knew, but brought up close, incredibly beautiful.

Beaked hazelnut (Corylus cornuta) fruit detail.©Devin Floyd

Given that our little walk was well under an hour’s time spent, and that I take this walk almost every day, what we discovered in detail was new to me, and serves to remind us all that the quest for discovery is never over.

-Scott Jackson-Ricketts

Photographs © Devin Floyd and Scott Jackson-Ricketts

The Summer "horn of plenty"

In walking around our farm in this late Summer period I am struck by the exuberant production of Nature including flowers, fruits, seeds, green vegetation, etc. I especially notice the fruits of the hackberry (likely Celtis occidentalis), which grows along one of our fence lines. This is not a species I see often although it is touted as a bird-friendly plant because of its fruits. We have tried planting it and its more southern relative the sugarberry, without a great deal of success. I think it requires a richer soil and more moisture than our sites generally provide.

Another beautiful and bird-friendly plant is the relatively rare cardinal flower (Lobelia cardinalis) which is highly specialized for pollination by hummingbirds. It has a very interesting ecology since it is a poor competitor with grasses and thus is found most often along streams, disturbed by occasional floods, or in wet areas of pastures where competition is reduced by grazing. It appears to be poisonous, as is ironweed, and is thus not eaten by horses. Ironweed is also one of our favorites due to its wonderful flowers and attraction to butterflies, and later to seed eating sparrows, such as the white crowned which spends Winters here on the farm.

Of course we should not ignore the growth of grasses and their abundant seeds which provide food for many animals. Indeed some herbaceous plants that farmers may consider weedy and less than desirable can be highly beneficial for wildlife. For example consider the foxtail (various Setaria species), grasses that flourish in Summer if the competition from cold-season grasses such as fescue is removed by cutting in mid-June. If you allow this to grow (we have a patch next to our garden) it will attract resident indigo buntings and even migrating bobolinks to harvest its seeds.

In contrast to this late Summer explosion of plant growth, most birds are past their breeding periods and are relatively quiet, many have begun migration, or are filling their bellies with the "horn of plenty" available all around them from the natural foods that have sustained them for eons. Given the luxury of such natural foods, it is very hard to justify artificial feeding of birds in the Summer. Let's try to balance our desire to enjoy birds in a backyard setting at feeders, with the best interests of the birds themselves. There is an alternative that can serve both the best interests of birds and their human watchers, namely the planting of appropriate native and exotic plants around our houses that provide foods in a manner consistent with natural patterns of behavior.

Bill Dunson
Galax, Va & Englewood, FL

Beware fuzzy caterpillars!

We have planted many hundreds of trees and shrubs on our property to encourage wildlife of all sorts, so I keep a careful eye out for pests that eat these plants. Some of the worse problems are due to insects that come in groups, such as caterpillars of various moths. I am used to dealing with army worms and web worms but came across a new enemy recently. Groups of hungry caterpillars appeared on our treasured black walnut trees (and sumac also) and started a full-scale attack (see photo above). In their young stage they were white with black spots and a black head, and were quite hairy. Now a fuzzy caterpillar often means "KEEP AWAY" since the hairs can be irritating and even toxic. These turned out to be hickory tussock moths or hickory tiger moths which are well known to possess stinging hairs and even to be toxic for birds to eat. They group together, likely with their siblings that hatched from their mother's eggs, and remain together for some time until they get much larger when they live alone (see photo below, of a much older caterpillar from our yard- not a typical coloration- often they are more black and white).
It is interesting to think about why not only insects but many types of animals group together in flocks or swarms. It is usually considered to be a defense, potentially to confuse and divert the attack of predators. In the case of these caterpillars, it is also likely that distasteful and/or toxic creatures ban together with siblings to gain an additional advantage if a predator does attack and learns to avoid this color pattern in the future. Siblings that share many of the same genes will benefit more by being together with their brothers and sisters than with strangers, if they are attacked and some are sacrificed to teach the predator to avoid the others.

Caterpillars have a variety of defenses other than stinging hairs and toxic flesh. They tend to be active at night and group together in daytime under protective webs. When I touched the leaf on which the young hickory tussock moths were sitting, a surprising thing happened- numbers of caterpillars began to drop down to the ground quickly on web lines (see photo). You might wonder why this would be necessary when these caterpillars seem to be so well protected. However virtually all good defenses have spawned a specialized predator that can circumvent the defensive strategy- in this case it is the yellow-billed cuckoo (see photo) which is a fuzzy caterpillar eater. Not coincidentally we have noticed far more cuckoos on our property this year than last when caterpillars were not so numerous. So the hickory tussock moth caterpillars drop from the tree at the slightest indication of a cuckoo being present, and can then crawl back into the tree after the cuckoo leaves.

The intricate natural history of something so seemingly inconsequential as a tiger moth caterpillar tells us once again that the adaptations of this larval moth are subject to very specific design criteria to maximize its chances of survival and subsequent reproduction. So even if we destroy some of these creatures that eat our yard plants, we cannot fail to marvel at their remarkable methods of existence.

Bill Dunson
Galax, VA & Englewood, FL

Exceptions to the Rule...identifying trees

In a recent attempt to learn more about trees I've found myself wading through the many ways they can be identified or distinguished from one another. One can look at the leaf scars, the leaves, the leaf buds, the bark, the tree shape, flowers, fruit, among others. In nearly all cases I find slight variations that make an accurate ID a challenge. some trees are young, some old, and some grow differently in different environments. If one were to spend time laying out the variety that exists in leaf shapes and proportions in a single tree, the complexity becomes apparent...especially if one attempts to compare the leaves of different species that are quite similar in appearance, like southern red oak, pin oak, northern red oak, and scarlet oak.
In this fog of confusion, one method works best for me. I use two or more attributes, always. In the following example I use the Sourwood tree (Oxydendrum arboreum), not for variety in leaves, but for variety in the bark. With the sourwood, I've been relying upon three attributes for confident wintertime ID: wispy seed strands (panicles) atop the trees, the distinctly patterned bark, and the unusual structure of the tree itself. In the photograph you'll notice that great variation can occur with a variation in size. The bark on your left is on a tree with a 4 inch diameter. The tree on the right had a diameter of 8 inches, and has bark that is much more coarse. Were it not for the distinct structure of the tree and the presence of panicles in the tree tops, an ID would have been difficult.
So, the take-away here is that one should never rely upon a single attribute for making an ID. The same can be said for using guide books as sources. Cross-referencing is essential when trying to understand the differences between tree species.
By the way, may favorite (and recently chosen) combination is Sibley (the newly released tree book) and Watts (Winter tree finder). The combo has given me renewed interest and confidence.
Happy tree watching!

Lava reaching skyward

This past Sunday, a group of us Charlottesville folk went to Humpback rocks up on the Blue Ridge (mile 5.8 on the Blue Ridge Parkway). We enjoy being within a twenty minute drive of these higher elevations...and we aren't alone. The parking lot was packed, and the nearby by living farm exhibit gets year around attention. The trip up there is always amazing because the landscape changes so dramatically before ones eyes...and your ears "pop". Interstate 64 climbs diagonally up the mountain cutting through thick deposits of metamorphosed lava. We were time travelers ...traveling forward in time to see denuded trees that will dominate our view down on the Piedmont in a couple of weeks; our trees are still hanging on to leaves...especially the oaks, hickories, and invasives (pawlonia, white mulberry, etc.). We were also traveling through a complex geologic landscape, ultimately ending up in meta-basalts deposited when central Virginia was well south of the equator, and turned 90 degrees east! (Check this map out)

We all met at the parking lot, the kids poured out, and off we went into a woods known for its high black bear population. Some estimates claim that 3 bear live upon every 2 square miles of woods....that's quite a bit. The nearby Shenandoah National Park boasts the largest population of black bears in the east. This is not the time of year to see them though...late spring and early summer is when you can catch them moving about as mating season kicks in.
An immediate thing noticed when one looks up from the parking lot is that a strenuous hike is about to be had. The hike covers over 1000 feet of elevation in less than a mile...with some mild rock climbing thrown in there. Half our kids had to be carried. The others had something else in mind....a race to the top!
We moved up the mountain, over outcroppings of 570 million year old Greenstone (young for Blue Ridge Rocks!). These rocks are old lava flows that once covered great amounts of what are today Virginia and Maryland. The rock is hard, very hard, and thus resists erosion. This greenstone holds up most of the peaks and ridges for most of the way thirteen miles south and over a hundred miles to the north.
The forest was dominated by Northern Red Oak, Chestnut Oak, and Hickory(mockernut, pignut, and shagbark). Sweet Birch, Witch Hazel, and Hophornbeam were the dominant understory trees. A few old field relics were scattered about in the forest, including large Flowering Dogwoods and Black Locusts, which were probably the oldest trees we saw at Humpback.
One of the familiar and signifying attributes of the dying black locusts is the polypore it plays host to, the Cracked Cap Polypore. So far as I know, it only grows on the Black Locust!

Along the trail we occasionally encountered enormous Chestnut Oaks. Check out the size of the one John's leaning on! Also notice the very distinct bark of the Chestnut oak...so deeply furrowed.

We also found several witchhazel in late bloom (see image with the inset), all but a few had dropped their long and wispy yellow petals and stamens, leaving behind these curved sepals.

All adults and kids (all five under the age of 5) made it to the top! I've tried this on two other occasions, without luck. Must have been somethin in the air! The view was magnificent.