Wednesday, October 24, 2012

The Wide View

Graduate students capturing images of the native grasslands
How often, on an absolutely perfect autumn day, do you have to spend the day outside as part of your job?  I know I rarely have that good fortune, but the stars were aligned on Monday, October 22.  That day, I escorted thirteen Rutgers University landscape architecture graduate students and their two advisers on a tour of the Pennypack Creek watershed.  The students' studio project this term is to develop a master plan for a watershed in central New Jersey.  The advisers were aware that the Pennypack  watershed has a long history of fairly sophisticated land use planning, natural resource conservation, and ecological restoration, so they brought the students to southeastern Pennsylvania to get a feeling for what can be done if government entities, nonprofit organizations, and municipal agencies can work in concert.

The upper third of the watershed has largely been given over to standard suburban development; much of it is already a "lost cause."  So, instead of starting at the source of the creek, we began the tour at the Pennypack Preserve in the central portion of the watershed and worked our way downstream over the course of the day.

After touring a portion of the protected land in the Pennypack Preserve and reviewing the forest restoration and native grassland creation projects underway, we enjoyed a picnic lunch then headed south into the city of Philadelphia for an overview of the lower third of the watershed.  Within the city, the creek flows through Pennypack Park, a protected corridor of parkland, but the corridor only protects the steep slopes directly alongside the stream, not the creek's tributaries.  Outside the park, development crowds right up to the edge of the woods.

Seasonal marsh occupying the site of a former parking lot
Our first stop in the city was at Verree Road where the road crossed the creek.  There, the park district had constructed a wet weather marsh a few years ago on the site of a former parking lot.  The parking lot was only usable part of the year because it was frequently flooded--either by stormwater overflowing from the adjacent creek, or from runoff in the watershed.  The park district scooped out the parking lot and replaced it with a seasonally-wet marsh.  The basin was dry on the day of our visit.

Residential stormwater outfall restoration project
Our second stop was at a stormwater outfall draining a large, mostly paved residential neighborhood in the Fox Chase section of the city.  The park district had recently completed an engineered restoration of the stream channel, replacing a severely eroded 12-foot-deep gully with a wider, boulder-lined swale designed to accommodate the stormwater outfall.  Further downstream, the park had installed a series of check dams and step pools to further slow and attenuate the flow before the stream re-entered its natural channel.  The engineered intrusion into the forest looks raw and unnatural, but the outfall becomes a raging torrent during heavy rains--like a water cannon blasting the streambanks--so anything less than a major retrofit would soon have washed away.

Check dams and step pools in the stream valley
Our third stop was at Frankford Avenue at the fall line--the line at which a stream "falls" off the hard edge of the continent (often at a waterfall or rapids) and flows out onto the unconsolidated sediments of the coastal plain.  The fall line also represents the landward limit of the tides; downstream of this point, Pennypack Creek becomes tidal.

Rapids at Pennypack Creek's fall line
Students at the fall line, with the Frankford Avenue (King's Road)  bridge in the background
Just a few hundred feet downstream of the fall line, the creek is spanned by the oldest bridge in the United States--the King's Road bridge, built in 1697.  The King's Road connected Philadelphia with New York.  The bridge (now known as the Frankford Avenue bridge) is still in use and bears a heavy load of vehicular traffic.

Our final stop of the day was on the coastal plain at the mouth of the creek at Pennypack on the Delaware.  Here, the creek adds its flow to the Delaware River, which is also tidal.  We arrived at low tide, and the mud flats flanking the mouth of the creek were fully exposed.  The wetlands around the mouth of the creek are home to a pair of Bald Eagles, which started building a nest two years ago and have fledged chicks successfully each summer since.

Mud flats exposed at Pennypack Creek's mouth at the Delaware River
The Philadelphia skyline, about seven miles distant
Students spread out in the maze of trails near the mouth of the creek to explore its wetlands.  As I came around a corner of a paved walking path, I found two students sprawled on the asphalt, clearly intent on something in the center of the trail.

A really hard day, or something exciting...?

They were getting up close and personal with a preying mantis that had caught a sulfur butterfly and was making quick work of the victim.

After we returned to our vehicles, I sent the students back to New Brunswick, New Jersey, and I headed back to the 'burbs.  A good day was had by all.

Submitted by 
David Robertson, Executive Director

Wednesday, October 17, 2012



My wife Mary and I set off for a walk when I got home from work yesterday (Tuesday) evening.  The weather was perfect for a walk in the Pennypack Preserve; we couldn't waste a classic autumn day.  Now that the sun is setting early, the light is perfect for photography in the late afternoon and early evening.  Last evening was no exception.

Just outside our door, we met a friend, Janet, who was walking the trails and birding.  We don't see Janet as often as we like, so we all set off together across the grasslands.

In a hollow along the Raytharn Trail, we came upon a pignut hickory (Carya glabra) in perfect fall color.

This hickory is a "wolf tree" wanna-be.  Wolf trees typically are mature, broad-crowned trees embedded within a younger woodland.  They originated when farmers left large trees in pastures to afford their cattle respite from the summer sun.  Becaue the trees were open-grown (i.e., not grown in a woodland where all trees grow tall and straight as they compete with their neighbors for light), these pasture shade trees developed expansive, broad crowns. Then, when farmers abandoned their pastures and natural succession turned the fields back into forest, the wolf trees became a part of the new woods, but always retained their distinctive form.  This hickory is not yet a true wolf tree since it still dominates a field that is fairly open, but invisible in the image, obscured by the russett grasses, are many, many saplings that Pennypack has planted to return this field to forest.  So, it's a future wolf tree.  (incidentally, since I know someone will wonder about the original of the term, these trees were so designated because, like proud wolves, they stand alone.)

Further along, we came to a popular viewpoint.  Across the creek, perched on the edge of the valley, is the Bryn Athyn Cathedral built during the Depression with an odd mixture of Gothic and Romaneque features.  In the setting sun, it was glorious.

And, as we were admiring the view of the cathedral across the valley, Janet noticed rustling at our feet.  There, she spotted a young American Goldfinch (Carduelis tristis) casually gleaning seeds from the native grasses.  All in all, a wonderful walk and a great way to top off the day.

Posted by David Robertson
Executive Director

Monday, October 15, 2012

Celebrating Autumn

I had to work Saturday afternoon, my third weekend in a row, but it wasn't too onerous.  I was chaperone for hayrides through the native grasslands in the Pennypack Preserve.  Despite a frosty start to the day, the afternoon turned out sunny and clear; as long as we stayed out of the shade, the weather was perfect to celebrate October.

I didn't notice any migrating raptors coursing southward overhead, but there were plenty of resident Turkey Vultures (Cathartes aura) enjoying the thermals  and Red-tailed Hawks (Buteo jamaicensis) sent skyward by the tractor, perhaps taking advantage of prey disturbed by the passing of the haywagon.

Red-tailed Hawk circling over the golden grasslands
During the last of the three hayrides, I saw three American Kestrels (Falco sparverius) kiting over the fields.  I haven't seen kestrels in quite a while, and to see three of them hovering in one location was a real treat.  It must have been good hunting for rodents or the abundant grasshoppers.

In addition to hayrides, the Trust also offered kids the opportunity to decorate pumpkins, get their faces painted with a Halloween theme, and to enjoy some cider and spice cookies.

Posted by David Robertson
Executive Director

Monday, October 8, 2012

A Burst of Milkweed

Fall colors in the meadows and grasslands are definitely on the wane, but the seeds of the common milkweed (Asclepias syriaca) are bursting forth from their split, dried pods.

Darkness is coming on so soon now (7:15 p.m.) that Mary and I have to walk before dinner.  So, last Friday evening immediately after work we completed a short traverse of the grasslands and found that one of the pods had scattered its seeds in a cluster.  The seeds got hung-up in some of the grasses instead of floating off across the landscape.  Either the wind eventually carried them off, or the weekend's rain dropped them onto the soil.  In either case, next year we hope there will be more milkweeds to feed the Monarch caterpillars.   

Some milkweeds in the fields are still mostly green (though showing unmistakable signs of senescence).  I checked them for late Monarch caterpillars but found none.  Our local Monarch Waystation tender says that she's still finding caterpillars on some of her milkweeds, but suspects that they won't be able to metamorphose in time to escape the frost.
Posted by David Robertson
Executive Director

Wednesday, October 3, 2012

Autumn Fog

For the last two days, a front has stalled over the northern Piedmont.  While we've had showers off and on, the front's most dramatic effect has been to envelope us in a soft, gauzy fog.

Last night, after an early dinner, enough light remained to entice me out into the fields to capture some of the muted landscape.

In some places, goldenrod (Solidago spp.) blooms are past their prime and beginning to turn brown...

...but in other places, they're still going strong.

A friend of mine, a Welsh ex-pat named Keith Collins, haunts the preserve taking pictures, too.  He shared some of his images from yesterday's foggy afternoon.

White-snakeroot (Ageratina altissima) and Indian-grass (Sorghastrum nutans) by Keith Collins
Kaleidoscope of autumn wildflowers by Keith Collins
Staghorn sumac leaves (Rhus typhina) by Keith Collins
As I neared the end of my walk, I came across this bumblebee preparing to spend the night under the protective overhang of a decurved goldenrod spike.

Submitted by David Robertson, Executive Director
Pennypack Trust