Spicebush Swallowtail – LIFE IN THE LOWER SUSQUEHANNA RIVER WATERSHED

June 4, 2025June 4, 2025

Soakin’ Up the Smoky Sun

With temperatures finally climbing to seasonable levels and with stormy sun filtering through the yellow-brown smoke coming our way courtesy of wildfires in Alberta and other parts of central Canada, we ventured out to see what might be basking in our local star’s refracted rays…

Dragonflies including this Black Saddlebags are now actively patrolling the edges of waterways and wetlands for prey and mates.

Here we see a pair of Common Green Darners flying in tandem…

A sunny day almost always brings out the reptiles, including these Painted Turtles…

and the invasive Red-eared Slider, a native transplant from the American midwest.

A really big Snapping Turtle will prey on almost anything, including other Snapping Turtles…

…but this one seems to be fascinated by something a lot smaller. Something like these juvenile Golden Shiners seen here schooling in the sun-drenched shallows.

Turtles aren’t the only reptiles thriving in the heat. Northern Water Snakes (Nerodia sipedon sipedon) take full advantage of a sun-drenched rock to warm up after spending time in the chilly water of a stream.

Butterflies like this Spicebush Swallowtail enjoy time in the sun, even while seeking out minerals in a patch of moist soil.

Woodchucks — After its siblings darted into the familial burrow upon our approach, this juvenile Woodchuck instead sought the attention of its nurturing mother. Unlike its brothers and sisters, perhaps this little groundhog isn’t afraid of its own shadow. Or does the smoky haze have the youngster all confused about what does and doesn’t constitute as a shadow? Well, we can’t help you there, but you have a whole eight months to figure it out!

May 4, 2025May 5, 2025

Six Flowering Woody Plants

Here’s a look at six native shrubs and trees you can find blooming along forest edges in the lower Susquehanna valley right now.

The Black Locust (Robinia pseudoacacia), a member of the pea or legume family (Fabaceae), can be a dominant pioneer plant of sunny successional habitats, particularly on poor soils. Nodules along its roots fix nitrogen to help facilitate the growth of the intermediate and climax species of trees and shrubs that replace the pioneers. Initially armed with protective spines to reduce browsing, the Black Locust’s branches become mostly thornless as the tree matures.

The Pinxter Flower, also known as the Pink Azalea, is certainly a contender for our most spectacular native blossoming shrub;…

Spicebush Swallowtail on Pinxter Flower — …this Spicebush Swallowtail seems to like it too.

When in bloom, the Black Cherry is a common sight in regional woodlands. Often seen already covered with blossoms when young and shrub-like, many of these trees will continue flowering and producing fruit throughout the decades required to reach a mature height of 60 feet or more.

The Blackhaw is an understory shrub preferential to sun-dappled areas beneath a break in the forest canopy. Pollinated flowers later produce clusters of blue-black berries for birds and other wildlife.

It’s easy to overlook the flowers of the Common Pawpaw. By the time the leaves are fully emerged and casting shade, blooming time is over.

Local old timers might remember hearing folklore that equates the northward advance of the blooming of the Flowering Dogwoods with the progress of the American Shad’s spring spawning run up the river. While this is hardly a scientific proclamation, it is likely predicated on what had been some rather consistent observation prior to the construction of the lower Susquehanna’s hydroelectric dams. In fact, we’ve found it to be a useful way to remind us that it’s time for a trip to the river shoreline below Conowingo Dam to witness signs of the spring fish migration each year. We’re headed that way now and will summarize our sightings for you in days to come.

September 11, 2023September 12, 2023

A Visit to a Beaver Pond

To pass the afternoon, we sat quietly along the edge of a pond created recently by North American Beavers (Castor canadensis). They first constructed their dam on this small stream about five years ago. Since then, a flourishing wetland has become established. Have a look.

A beaver lodge. — The beaver lodge was built among shrubs growing in shallow water in the middle of the pond.

Woolgrass in a beaver pond. — Woolgrass (Scirpus cyperinus) is a bulrush that thrives as an emergent and as a terrestrial plant in moist soils bordering the pond.

A male Common Whitetail dragonfly keeping watch over his territory.

A Twelve-spotted Skimmer perched on Soft Rush.

A Blue Dasher dragonfly seizing a Fall Field Cricket (Gryllus pennsylvanicus).

A Spicebush Swallowtail visiting Cardinal Flower. — A Spicebush Swallowtail visiting a Cardinal Flower.

A Green Heron looking for small fish, crayfish, frogs, and tadpoles.

A Green Heron stalks potential prey. — The Green Heron stalking potential prey.

A Wood Duck feeding on Lesser Duckweed. — A Wood Duck feeding on the tiny floating plant known as Lesser Duckweed (Lemna minor).

A Least Sandpiper feeding along the muddy edge of a beaver pond. — A Least Sandpiper poking at small invertebrates along the muddy edge of the beaver pond.

A Solitary Sandpiper testing the waters for proper feeding depth.

A Pectoral Sandpiper searches for its next morsel of sustenance.

A Sora rail in a beaver pond. — The Sora (Porzana carolina) is a seldom seen rail of marshlands including those created by North American Beavers. Common Cattails, sedges, and rushes provide these chicken-shaped wetland birds with nesting and loafing cover.

Isn’t that amazing? North American Beavers build and maintain what human engineers struggle to master—dams and ponds that reduce pollution, allow fish passage, and support self-sustaining ecosystems. Want to clean up the streams and floodplains of your local watershed? Let the beavers do the job!

March 3, 2023August 14, 2023

Plantings for Wet Lowlands

This linear grove of mature trees, many of them nearly one hundred years old, is a planting of native White Oaks (Quercus alba) and Swamp White Oaks (Quercus bicolor).

Imagine the benefit of trees like this along that section of stream you’re mowing or grazing right now. The Swamp White Oak in particular thrives in wet soils and is available now for just a couple of bucks per tree from several of the lower Susquehanna’s County Conservation District Tree Sales. These and other trees and shrubs planted along creeks and rivers to create a riparian buffer help reduce sediment and nutrient pollution. In addition, these vegetated borders protect against soil erosion, they provide shade to otherwise sun-scorched waters, and they provide essential wildlife habitat. What’s not to love?

The following native species make great companions for Swamp White Oaks in a lowland setting and are available at bargain prices from one or more of the County Conservation District Tree Sales now underway…

The Red Maple is an ideal tree for a stream buffer project. They do so well that you should limit them to 10% or less of the plants in your project so that they don’t overwhelm slower-growing species.

The River Birch (Betula nigra) is a multi-trunked tree of lowlands. Large specimens with arching trunks help shade waterways and provide a source of falling insects for surface-feeding fish. Its peeling bark is a distinctive feature.

The Common Winterberry with its showy red winter-time fruit is a slow-growing shrub of wet soils. Only female specimens of this deciduous holly produce berries, so you need to plant a bunch to make sure you have both genders for successful pollination.

American Robins feeding on Common Winterberry. — An American Robin feeding on Common Winterberry.

Common Spicebush is a shrub of moist lowland soils. It is the host plant for the Spicebush Swallowtail butterfly and produces small red berries for birds and other wildlife. Plant it widely among taller trees to provide native vegetation in the understory of your forest.

Common Spicebush foliage and berries. — Common Spicebush foliage and berries in the shade beneath a canopy of tall trees.

The Buttonbush is a shrub of wet soils. It produces a round flower cluster, followed by this globular seed cluster.

And don’t forget the Eastern Sycamore, the giant of the lowlands. At maturity, the white-and-tan-colored bark on massive specimens makes them a spectacular sight along stream courses and river shores. Birds ranging from owls, eagles, and herons to smaller species including the Yellow-throated Warbler rely upon them for nesting sites.

Yellow-crowned Night Herons Nesting in an Eastern Sycamore — Yellow-crowned Night Herons, an endangered species in Pennsylvania, nesting in an Eastern Sycamore.

So don’t mow, do something positive and plant a buffer!

Act now to order your plants because deadlines are approaching fast. For links to the County Conservation District Tree Sales in the Lower Susquehanna River Watershed, see our February 18th post.

September 13, 2017September 4, 2019

Living in the Shadows

They get a touch of it here, and a sparkle or two there. Maybe, for a couple of hours each day, the glorious life-giving glow of the sun finds an opening in the canopy to warm and nourish their leaves, then the rays of light creep away across the forest floor, and it’s shade for the remainder of the day.

The flowering plants which thrive in the understory of the Riparian Woodlands often escape much notice. They gather only a fraction of the daylight collected by species growing in full exposure to the sun. Yet, by season’s end, many produce showy flowers or nourishing fruits of great import to wildlife. While light may be sparingly rationed through the leaves of the tall trees overhead, moisture is nearly always assured in the damp soils of the riverside forest. For these plants, growth is slow, but continuous. And now, it’s show time.

So let’s take a late-summer stroll through the Riparian Woodlands of Conewago Falls, minus the face full of cobwebs, and have a look at some of the strikingly beautiful plants found living in the shadows.

Oxeye *(Heliopsis helianthoides)* is common on the interior and along the edges of Riparian Woodland. Specimens in deep shade flower less profusely and average less than half the height of the five feet tall inhabitants of edge environs.

Pale Touch-Me-Not *(Impatiens pallida)* is one of two species of native *Impatiens* found in the river floodplain. Both are known as Jewelweed. The stems and leaves of the indigenous Impatiens retain a great quantity of water, so life in filtered sunlight is essential to prevent desiccation. Contrary to popular folklore, extracts of Jewelweed plants are not effective treatments of Poison Ivy *(Toxicodendron radicans)* contact dermatitis.

Spotted Touch-Me-Not *(Impatiens capensis)* is typically found in wetter soil than *I. pallida*. Both Jewelweeds develop popping capsules which help to distribute the seeds of these annual wildflowers. “Touch Me Not”, or you’ll be wearing tiny seeds.

Green-headed Coneflower *(Rudbeckia laciniata)* grows to heights of eight feet in full sun, hence its alternate common name, Tall Coneflower. In deep shade, it may not exceed two feet in height. Floodplains are the prime domain of this perennial.

Wingstem *(Verbesina alternifolia)* normally flowers no earlier than late August. The bases of the leaves are continued onto the stem of the plant to form wings which extend downward along its length. This wildflower tolerates shade, but flowers more profusely along the woodland edge.

Great Lobelia *(Lobelia siphilitica),* or Great Blue Lobelia, is a magnificent wetland and moist woodland wildflower, usually attaining three feet in height and adorned with a plant-topping spike of blossoms. Invasive Japanese Stiltgrass *(Microstegium vimineum)* can be seen here competing with this plant, resulting in a shorter, less productive Lobelia. Stiltgrass was not found in the Susquehanna River floodplain at Conewago Falls until sometime after 1997. It has spread to all areas of woodland shade, its tiny seeds being blown and translocated along roads, mowed lots, trails, and streams to quickly colonize and overtake new ground.

American Bladdernut *(Staphylea trifolia),* a shrub of shaded woods, develops inflated capsules which easily float away during high water to distribute the seeds contained inside.

Buttonbush *(Cephalanthus occidentalis)* is a shrub of wet soils which produces a strange spherical flower, followed by this globular seed cluster.

Common Pawpaw (Asimina triloba) is a colony-forming small tree which produces a fleshy fruit. It is the host plant for the caterpillars of the Zebra Swallowtail. The plant and the butterfly approach the northern limit of their geographic range at Conewago Falls.

Common Spicebush *(Lindera benzoin)* is a widespread understory shrub in wet floodplain soils. It is the host plant for the caterpillars of the Spicebush Swallowtail *(Papilio troilus)*.

Sweet Autumn Virgin’s Bower *(Clematis terniflora)* is an escape from cultivation which has recently naturalized in the edge areas of the Conewago Falls Riparian Woodlands. This vine is very showy when flowering and producing seed, but can be detrimental to some of the understory shrubs upon which it tends to climb.

SOURCES

Long, David; Ballentine, Noel H.; and Marks, James G., Jr. 1997. Treatment of Poison Ivy/Oak Allergic Contact Dermatitis With an Extract of Jewelweed. American Journal of Contact Dermatitis. 8(3): pp. 150-153.

Newcomb, Lawrence. 1977. Newcomb’s Wildflower Guide. Little, Brown and Company. Boston, Massachusetts.