Sun-Loving Prairie Wildflowers of Glennstone

Walking along the trails of ECWA's nature preserve at Glennstone, downstream from Durham, out towards Falls Lake, you will find many wildflowers that still flourish where trees have yet to cast their shadow. In the first photo is Carolina rose (Rosa carolina), a low-growing rose common at Glennstone. My most memorable encounter with this flower was in the middle of a very hot day when the landscape had already been parched by severe drought. Fortunately, I "stopped to smell the roses", and was rewarded by a fragrance sweet and soft, refreshing as a cool drink after a long trek through the desert.

Snowdrops, a kind of primrose, is another bright flower in May.

The last photo is of Round-Headed Bushclover, the native wildflower at Glennstone that I have encountered growing nowhere else in all my travels. It's discussed in a previous post on this website.

Native Flowers Near the Landfill

One of the richest deposits of irony paradoxide in the Ellerbe Creek watershed is at the Durham city landfill, which was closed some years back and planted with grass to protect the clay cap carefully spread over several decades' worth of Durham's garbage.

People tend not to have fond associations with landfills, but this one is an extraordinary landscape. Essentially a mountain, it boasts an extraordinary panoramic view of Durham county. Watching a glorious sunset there years back, I saw fifteen wild turkeys foraging just down the slope. Many years ago, during a tour, while the landfill was still in operation, a city councilwoman who had recently returned from Africa gazed out across the side of the landfill, turned bronze by broomsedge grass in the winter, and said it reminded her of the Serengeti. At the time of its closure, residents living nearby had requested that it be turned into something akin to a botanical garden. Currently, the landfill is not open to the public.

Though the landfill is a profoundly altered landscape, along its edges are some of the best preserved remnants of Durham's natural heritage, as can be seen in the first photo. Looking across a beaver pond, you can see the landfill rising in the distance. But in the foreground is a pinxter azalea, a beautiful native shrub that is rarely seen in the watershed.


Growing near the azalea is a patch of blue crested iris, which, if one can judge by the ten foot wide clone, has been growing there a very, very long time.


Viburnum dentatum (3rd photo) is another of the less common natives growing there. Their prevalence suggests that the small slope next to the beaver pond was never plowed.


Very close by is another rich remnant of native plant diversity, also on city land. Though it looks like a plain bit of roadside grass under a powerline (fourth photo), it in fact harbors 111 native species of wildflowers and grasses, including big bluestem--the dominant grass of the tall grass prairies in the midwest.

Most people don't know that bison once lived in what is now North Carolina (traces of a bison migration route can still be found north of Durham), or that in precolonial times the piedmont was a mosaic of forest and prairie.

Remnants like this one near the landfill, which survives only because roadsides were left unplowed and trees are prevented from growing under powerlines, serve as valuable windows into an extraordinary past. Because this remnant is biologically special and irreplaceable, ECWA officially adopted it some years ago, through an arrangement with Duke Energy, to prevent it from being sprayed with herbicides. ECWA maintains the site by cutting down any tree growth.


One of the unusual wildflowers growing in this roadside prairie remnant is leather flower (Clematis ochroleuca). Unlike the clematis we're accustomed to seeing, this species is not a vine but instead stands erect. Leather flower is one of a number of rare wildflowers in the piedmont that only grows on a soil called diabase, named for the characteristic rock from which it forms.

The sustainability of this site's rich botanical legacy would be greatly enhanced by expanding it into the adjacent city-owned land.

A Detention Basin Becomes a Wetland

Neighbors weren't too happy when a large swath of land was cleared to make this detention basin. The developer, who had long wished there were a way to make these government-required stormwater features more attractive, was sympathetic to the homeowners' strident complaints.



With the help of the Ellerbe Creek Watershed Association (ECWA), to which the developer had donated 82 acres adjoining the new subdivision, a plan came together to transform the unsightly detention basin into a wetland full of native wildflowers.

This all sounds well-intended--the sort of ambitious project that would never quite come to fruition--but in this case everyone involved followed through. ECWA provided a detailed plant list. The developer designed and installed a walkway and pergola overlooking the basin, and paid a landscaper to do the planting. Volunteers from ECWA worked with neighbors to plant additional native grasses and shrubs on the slopes, which had previously been seeded with annual grass to prevent erosion.

The last two photos show the basin in May of 2008, as it began its third growing season. The basin has in fact been transformed into a wetland, with soft rush, pickerelweed, cattails and other native plants.

The one less than ideal aspect is that the cattails will likely take over the whole basin unless controlled in some way. But having gone into the project with both enthusiasm and some skepticism about whether such a feel-good transformation, from ugly pit to verdant wetland, could actually be achieved, I'd have to say the it's been a great success.

Nature and Culture at Glennstone Preserve

Just to the west of the preserve, at the end of Davie Drive, is an impressive assemblage of antique vehicles and farm equipment rusting in the sun. Some would consider them a blight on the landscape. I see them as historic scuptures, evidence of the lower valley's past, mixing with the rushes and cattails that thrive in the wet ground. The tradition of mixing sculpture and garden is alive and well in the piedmont, whether at the N.C. Botanical Garden some fifteen miles to the south, where the sculptures are actually intended, or in this casual juxtaposition in the lower Ellerbe Creek watershed.

In the second photo, Bushclovers and Eupatoriums thrive in the sunlight above a sewer line that runs underground through the preserve. Long ago, these wildflowers would have grown where periodic fire limited tree growth. Now, with fire banished from the landscape, these shade-intolerant species survive only where trees are prevented from growing--along roadsides and sewer right of ways.

Healing Construction Wounds at Glennstone

This detention basin caught sediment from the Glennstone housing development during construction. After the houses were up, it was left to be reclaimed by whatever would grow there. Some seeds were already in the soil from years or decades past. Others came in by bird, wind or stormwater.

In the foreground of the first photo is one pleasant surprise--passion flower, a vine that spreads underground and sends up shoots each year with beautiful, incredibly complex flowers.

In the second photo is Butterfly Pea, a native legume with large pink flowers that crawls along the ground.

These first two plants prefer the dry ground on the berm. The last photo shows Woolgrass, an attractive native sedge that thrives in the low spots still fed by runoff from yards up the hill.

An Old Spring at Glennstone Preserve

Just down the hill from the remains of a summer cottage, next to a rocky creek, is the remains of a spring where the owners of the cottage must have gotten their water. A small pipe sticks out of this half circle of stone, near the bottom. The ground there is consistently wet, but I've never seen water actually flowing out of the pipe. Perhaps there's a way to clean out the spring and allow it to flow again.

Within a few feet of the spring grows a JoePyeWeed, a tall wildflower found nowhere else in the preserve. Apparently, the stable water source allowed the plant to survive droughts.

Glennstone Notes for Signage

Concept 1 for Sign: What makes Glennstone Preserve special?

I. GEOLOGY:

DIABASE GLADES (Jurassic Diabase in Triassic Basin, Iredell soils)

Following excerpt from A GEOLOGIC ADVENTURE ALONG THE ENO RIVER-Information Circular 35 by NC Geologic Survey (p.25):

DIKES AND SILLS INTRUDE THE TRIASSIC BASIN AND INTO CAROLINA TERRANE ROCKS

MAFIC magma from deep in the earth welled up through fractures in the crust at the beginning of the Jurassic period (approximately 195-205 million years ago). This magma intruded the sediments of the Triassic basin and surrounding crystalline rocks of the Carolina terrane. At the same time, to the east of the Durham Triassic basin, the main rift separating the North American and African continents was growing, causing the continents to slowly move away from each other. Mafic magma also welled up through the main rift zone, known as the mid-Atlantic ridge, and provided the raw material for the expanding ocean basin. In the Durham Triassic basin, the magma solidified into rock known as diabase. Diabase is a mafic rock with a composition similar to ocean floor basalts.

In the Durham Triassic basin, diabase is more resistant than surrounding sandstones and siltstones it intrudes and often forms resistant ridges in the Durham area. Penny’s Bend on the Eno River is underlain by diabase. Diabase is composed of minerals that contain abundant iron and magnesium in comparison to the Triassic sediments. Because of the abundance of iron and magnesium, unique plant communities sometimes develop on top of areas underlain by diabase (e.g. The Diabase Glades).

My note: I included this because it so well explains, with the aid of a geological map that is included in this circular, diabase glades. (You can even see sills on Glen Road near Club Blvd. on this map!) Of course, it is way too complex for interpretive sign but helpful perhaps when writing concepts, geological timeline or maps.

2. PLANT COMMUNITIES:

A. TWO TYPES OF UNUSUAL (for Piedmont) PLANT COMMUNITIES: PRAIRIE/MEADOW AND POST OAK FOREST. (we need to check the Natural Heritage Program's description of plant communities to see which ones fit Glennstone)

B. MORE DIVERSITY PLANTS WITHIN COMMUNITIES, due to north-facing slope, lack of plowing, and presence of diabase soils.

3. GLENNS HOMESITE:

1. FIRST(?) COLONIAL SETTLEMENT (Old homesite ruins may be nearby)
2. LARGE PIECE OF NORTH SLOPING LAND RELATIVELEY UNDISTURBED (logged in last decades of 1900’s, but not plowed or developed). This affected swift return to forest saplings. Other factors can affect and interrupt successional stages as well….

4. PROXIMITY TO ELLERBE CREEK AND Alluvial corridor of MATURE FOREST extending down to and around Falls Lake. Provides intact corridor for wildlife.

5. PROXIMITY TO HERON ROOKERY.

6. Borders Glenn Cemetery, with headstones dating back to 1700s.

Concept 2 for Sign

The second potential concept for the interpretive sign would focus on succession, but not present succession as an inevitable shift from herbaceous to mature forest, but instead use a double arrow (a two-way street, essentially) between prairie and forest, with natural forces such as fire, along with anthropogenic forces like logging and mowing, pushing the plant community towards prairie, while successional forces push towards trees.

We can point out that some areas are resisting tree growth on their own--most likely due to stronger diabase characteristics in the soil that discourage tree growth.

What Makes the Glennstone Preserve Special

The Glennstone Nature Preserve, owned and managed by the Ellerbe Creek Watershed Association in Durham, NC, is made special not only by what lies within its borders, but also what can be found close by.

The plants are more diverse than usual at Glennstone in part because much of the preserve slants down towards the north. A "north-facing slope" is more protected from the sun's rays, and so stays more evenly moist through the year. This helps many kinds of plants survive that would otherwise die out during harsh droughts.

The soil here is also special. Glennstone contains large areas of diabase soil, which is less acidic than other piedmont soils. Some of the rarest plant species in North Carolina grow only in this soil type. Because this soil type was not believed to be good for farming, much of the preserve was spared the plow, which would otherwise have obliterated the native plants. The preserve does contain two small fields that once were farmed, containing much less plant diversity than the unfarmed areas.

Glennstone also has two rock-strewn tributaries of Ellerbe Creek flowing through it. The remnants of a cottage dating back to the 19th century (?) can be found on a bluff overlooking one of the creeks, with an old spring nearby.

But the quality of any preserve is affected by what surrounds it. In this regard, Glennstone is especially lucky. Just to the north of the preserve, Ellerbe Creek flows through federally owned mature floodplain forest on its way to what is now Falls Lake (formerly the Neuse River). Like all waterways, Ellerbe Creek serves as an important wildlife corridor, and Glennstone no doubt gets visited frequently by wildlife moving up and down the creek. Pileated woodpeckers have been seen in the floodplain woods. There's been evidence of bobcats coming through. Woodcocks do their spring mating flights in the more open areas of the preserve, and quail were common in the years after logging and before trees began once again to claim the land.

You may have seen large birds with folded necks overhead, flying steady and straight. These are great blue herons, coming and going from their roosts in tall trees on city land just to the west of the preserve.

Also just west, on a bluff overlooking the preserve, is the Glenn Cemetery, where headstones date back to the 18th century.

Native and Exotic Bushclovers at Glennstone

Found nowhere else in the Ellerbe Creek watershed, the Round-Headed Bushclover (Lespedeza capitata) is a special plant species in the Glennstone Preserve. Needing lots of sunlight to prosper, it grows in clearings and especially along the sewer line right of way, which is a utilitarian name for a very attractive ribbon of grasses and wildflowers that threats through the preserve. The right of way is kept free of trees to allow access for maintenance of the sewer line buried beneath.

The large seeds of Round-Headed Bushclover are an important food for quail, wild turkey and mourning doves.







In the fourth photo you can see seeds from three kinds of bushclover at Glennstone. The largest, upper left in the photo, are from the round-headed bushclover. The next largest are from Slender Bushclover (Lespedeza virginica), which is also a native.

The smallest seeds in the photo are from a highly invasive exotic called Sericea Lespedeza (Lespedeza cuneata). Originally planted by the Dept. of Transportation for erosion control, it is now considered a noxious weed in 46 states. Though its seeds were thought to be good for wildlife, it is now believed that its small seeds move through birds undigested.

The exotic lespedeza has been invading the Glennstone Preserve along the sewer line, and is aggressive enough to completely displace the native bushclovers that wildlife need for food. ECWA has been working to eradicate this noxious weed from the preserve before it does more damage. The exotic lespedeza has a white flower, which is useful in distinguishing it from the pink-flowered native Slender Bushclover (last photo).



More information about the Round-Headed Bushclover can be found at http://www.illinoiswildflowers.info/prairie/plantx/rh_bushcloverx.htm