This blackjack oak (Quercus marilandica) was found on one of southeastern Missouri’s finest sand prairie relicts a couple of weeks ago on my ‘Annual Birthday Season Opener Bug Collecting Trip.’ Growing near the edge of the prairie at the transition to dry sand forest (Nelson 1985), the arrays of soft, red, newly-expanding leaves at each branch tip had a distinctly floral quality to them. Of course, as with all oaks, the actual flowers of blackjack oak are much less conspicuous, with the staminate (male) flowers borne on drooping catkins, the pistillate (female) flowers on separate spikes on the branch, and pollination accomplished by wind.
Missouri is oak country – nearly a quarter of North America’s 90 oak species (Nixon 2009) occur naturally within the state. This high diversity is explained partly by Missouri’s ecotonal continental position – straddling the east-west transition from the great eastern deciduous forest to the western grasslands. The boundary between these two great biomes is a dynamic, ever-changing interdigitation of woodland, savanna, and prairie that ebbs and flows with the prevailing climatic conditions. Unlike the more mesic forests further east, these dry woodland habitats were often subjected to fire during presettlement times – to which oaks in general (and blackjack oak in particular) are supremely adapted with their thick bark and ability to resprout repeatedly after being burned or grazed back. Sadly, the suppression of these fires post-settlement has caused many of these unique, fire-mediated natural communities to shrink drastically amidst a choking growth of junipers (“cedars” ’round these parts), maples, and other fire-intolerant species. Only on publicly owned preserves and a few private parcels under progressive ownership (such as the sand prairie relict where this photograph was taken) is fire once again shaping the landscape.
Oaks are among my favorite trees, and among the oaks I have several favorites. White oak (Quercus alba) – tolerating many forest types but forming nearly pure stands in high-quality, mesic sites, its tall symmetrical crown, pale bark, and brilliant fall colors are unparalleled among Missouri’s other oaks. Post oak (Q. stellata) as well – lacking the elegance of white oak but achieving its greatest character in fire-adapted savannas and open woodlands as squat, gnarled, massively-trunked trees with broad, spreading crowns¹. Blackjack oak has none of these qualities, yet somehow, it is still one of my favorite Missouri oaks. Stunted and gnarled (‘scrub oak’ to some), it occurs mostly in sandstone and limestone glades, savannas and woodlands on dry, nutrient-poor soils that support few other tree species. The dark green of its tough, waxy (to limit the loss of water), pear-shaped leaves contrasts beautifully with its rough, blocky, almost black bark. Blackjack oak has virtually no timber value, although it is sometimes used for charcoal and firewood. Nevertheless, for me, it is almost an icon for the unique natural communities in Missouri in which it occurs – communities that face ever-increasing pressure from human and forest encroachment.
¹ Please refer to this lovely essay about post oaks in Missouri, by the talented Allison Vaughn.
Nelson, P. W. 1985. The Terrestrial Natural Communities of Missouri. Missouri Natural Areas Committee, Jefferson City, 197 pp.
Nixon, J. C. 2009. Quercus in Flora of North America, Vol. 3.
Copyright © Ted C. MacRae 2009