Tuesday, December 09, 2008
I distinctly remember the July afternoon when I grabbed the smooth gray branch covered in glossy green leaves and yelled at my colleague (stooped down over a sedge): "is this possumhaw?" Having known the deciduous holly from years spent down south in swampy backwater regions, I was stumped, truly perplexed to find it here, perched as it was on a limestone bluff in the middle of the dry, dry White River Hills of southwest Missouri.
Of course, it wasn't the first time that I stood utterly confused over a plant growing on a limestone glade. These dry, rocky outcroppings harbor a whole host of restricted plants, including the brilliant, charismatic Trelease's larkspur (bright, vibrant blue flowers!). This spring, we found a population of stunted ninebark, a charming little understory tree found primarily in moist woodlands, in full flower on a limestone glade. I did precisely the same thing upon both discoveries: I stood there, grasping branches of these plants, wondering if I had lost my mind or if they were really growing on glades. That day in the natural area, I learned that a certain plant that grows in bottomland hardwood forests of the southeastern U.S. can grow just as well on a rocky limestone or dolomite glade in Missouri. It's the exception, of course, and not the rule.
In Missouri, deciduous holly (Ilex decidua) is known from southeast Missouri, Mississippi River Valley floodplains, and Ozark regions based in limestone and dolomite substrates. As represented in its common name, deciduous holly loses its green leaves each year, thus exposing shiny red berries that persist into the winter months. Winter bird populations (Eastern bluebirds in particular) relish the nutritious berries found on possumhaw. Heading towards Columbia on the dolomitic regions of the Outer Ozark Border, fencerows are lined with possumhaw shrubs. They're so common, in fact, that they're characterized as "weedy."
In full sun, possumhaw branches burst forth with berries, covering every inch of bark. Because my nagging running injury persists (1 month, 3 days, 8 hours) and I still can't walk up inclines (or run, or drive without pain, or walk more than four blocks at a time), I was unable to see the brilliant red berries on top of the Butler Hollow Glades Natural Area outside of Cassville, Missouri this year. Instead, I rely on a dim photo taken in August from deep within a moody bottomland forest in southeast Missouri to express the subdued beauty of this shrub. (Berries occur in greatly diminished populations in the understory.)
So what are the requirements that allow possumhaw to thrive in thick, mucky soils of the Mississippi Embayment as well as dry, rocky glades of the Ozarks? Is it the low acidity of the soils? Is it the substrate? The esteemed Julian Steyermark doesn't provide an answer, and because the plant isn't particularly cherished by anyone but gardeners in Louisiana, I doubt anyone has investigated it. I can't get around anywhere these days, so I'll see what I can find out.
Posted by Allison Vaughn at 10:29 PM