Despite recent temperature plunges, some summer and early-fall flora are still blooming. Last week, my friend Robin Williams and I decided to see what was still in bloom and what had gone to seed in a Piedmont mafic prairie in southern Culpeper County.
“Mafic” refers to the mineral content of the soil at the site. According to the Virginia Department of Conservation and Recreation’s website, mafic denotes large amounts of dark-colored silicate minerals rich in magnesium and ferric, from which the term was formed. “Prairie,” as defined by DCR, is an herbaceous community dominated by warm-season perennial grasses and often containing other species that occur in Midwestern grasslands.
The only prairie-like natural communities that remain in the Virginia Piedmont, says DCR, are similar to this site in that they are “semi-natural and influenced by artificial disturbance regimes.” The disturbance regime at that spot, which is along a powerline right-of-way, is mowing by the Virginia Department of Transportation. Similar natural communities have also developed at Manassas National Battlefield Park.
Fires, such as those that occur at military training grounds, can also keep these prairies from turning into forest. Such sites are our “only examples of grassland vegetation that has been shaped by random burns of a size, frequency, and intensity” comparable the fire management believed to have been practiced by Virginia’s Native American tribes before the Europeans arrived here, according to DCR. These prairies offer a chance to see some plants that are now scarce in the Old Dominion. (To learn more about these grasslands, search on “piedmont prairie” on DCR’s website.)
On the walk, Robin and I found most of the flowering plants’ blooms had done their job of attracting pollinators and had gone to seed. While we figured it would at least be an easy walk on a relatively cool day, we could have picked a better time of day. Arriving in early afternoon, we found the weather surprisingly warm, with the sun glaring down at us in that shadeless open space.
The glare of midday is also not the perfect light for taking photographs, but I wasn’t looking for “pin-up’ shots of these plants. Most photographers, including me, concentrate on photographing flowering plants in full bloom because that’s usually when they’re at their most beautiful and most recognizable. It’s hard to find photos of plants before or after their bloom times, which makes identifying them in those seasons. Recently I’ve tried to shoot flowering and other plants in various seasons, and also photograph more than the bloom, including stems and leaves, to help with identification, especially when using references based on dichotomous keys, in which you work through steps choosing one of two options.
Robin, who is on the board of the Piedmont chapter of the Virginia Native Plant Society (VNPS), helped me sort out the species. The chapter had hosted a walk there in September, when more of these plants were in bloom. Robin had attended; I had a previous commitment.
I’d brought the useful plant list that the chapter had supplied for the walk, which included more than 50 species of plants that grow in Piedmont mafic prairie. I’d downloaded photos for each species, trying to include photos taken at this time of the year showing dried seed heads and other fall characteristics.
Some of the plants we identified on the walk were familiar to me, including narrow-leaf mountain mint, which I have in my pollinator garden. Its lovely small blossoms, white with lavender spots morph into gray seed heads this time of year. Some species of goldenrod also looked familiar, but most on the VNPS did not. Plants that definitely were new to me included rosin weed (Silphium asteriscus), the last of its yellow blooms fading, and seedbox (Ludwigia alternifolia), which got its name from its unusual square seed pods. We also found milkweed bugs on the open seed pods of dogbane, also known as Indian hemp (Apocynum cannabinum), a member of the huge Apocynaceae plant family, which also includes milkweeds. I spotted what I thought was frost aster (Symphyotrichum pilosum) in bloom, but this was not on the list, while a very similar species, bushy aster (S. dumosum) was. Both look a lot alike and bloom at the same time (August through October). Having not brought a guide to key out the ID, I took some photos and hope to determine the species at some point. Several species of native grass also grow on the site, including Indian grass (Sorghastrum nutans), which Robin pointed out to me.
Although the photo ops that day weren’t spectacular in the mostly brown landscape, got some shots that were useful for species identification. And Robin and I both agreed the site, with its diversity of grassland plants, would be worth revisiting next spring and summer, when it should be lush with blooms.
© 2015 Pam Owen
Plants of the Piedmont mafic prairie
Plants (by common name) on VNPS’ list for the Piedmont mafic prairie in southern Culpeper County include: Asters, axil flower, beaksedge, bean, tickseed sunflower, bindweed, blazing star, bluets, bush-clover, chicory, coreopsis, cuphea, dogbane, sweet everlasting, sweet, rabbit tobacco, false fox-glove, gaura, goldenrods, horse nettle, ironweed, jewelweed, Joe pye weed, lion’s foot, mountain mint, partridge pea, pennyroyal, pineweed, pussytoes, Queen Anne’s lace, ragweed, pasture rose, rosin weed, seedbox, self-heal, silverrod, spurge, St. Andrew’s cross, St. John’s wort, field thistle, throughworts, tick trefoil, lettuce, post oak, poison ivy and native grasses, including little bluestem, bottlebrush, joint-head, Indian, panic and wild rye.