Blackjack oak “flower”


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

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7 thoughts on “Blackjack oak “flower”

  1. I too am a lover of oaks! Thus, I must point out, Ted, that you short-changed them.

    According to this article (a fun read for oak nerds), there are 89 oak species in the US. I’m not sure why there is such a disparity between this article and the Flora of North America, but according to the latter, there are 149 species taxa in the genus Quercus in North America north of Mexico, almost 100 more than the figure you gave. 89 US species or 149? Either way, I’ll take it.

    By the way, the above cited article also states that the entire Mexico+US+Canadian flora contains 194 species, with fully 140 of these occurring in montane Mexico. Gotta get down there!

    And speaking of blackjack oaks, I have heard that the persistent dead lower limbs and branches make convenient kindling for campfires in all but driving rain.

    Also, could it be that you like blackjack oaks because they live in good tiger beetle habitat!

    • Yes, James. I did short-change the North American diversity. I thought 56 species sounded low and can’t recall now where I got that number, but that’s what I get for doing a quick internet search instead of going straight to my trusty, authoratative sources such as the two you mention. The appropriate edits have been made.

      Incidentally, as far as I can tell, FNA lists 90 species – pretty darn close to the 89 species given in Nixon’s 2002 paper that you cite (which I do have and thoroughly enjoyed – we’re such geeks!). Where did you see 149 for FNA (of which, incidentally, Nixon is also the author).

      Quercus in Mexico is surely unbelievable, but what I’m dying to see down there are some of the endemic pines – especially the Mexican blue, or Martinez, piñon (Pinus maximartiezii) – cones up to ten inches in length and four pounds in weight when green, with inch long nuts! You can read a fantastic account of one man’s search for this extraordinary pine at one of my favorite blogs, Watching the World Wake Up (part 1 of 6).

  2. I got the larger figure from adding together the number of taxa keyed out by the three subgenus keys in FNA. Better go back and check that figure, eh?

    • Hmm, interesting. At any rate, the main Quercus page states, “Species ca. 400 (90 in the flora)…” Maybe you counted one of the subgenera twice 🙂

      My love of blackjack oak is even more surprising given the fact that my attempts to rear woodboring beetles from it have been almost completely unsuccessful. I think you’re right – it’s more of a symbol for some of the habitats that I truly love.

  3. Beautiful picture- I didn’t quite realize how many species were native to Missouri. I’ve been planting many tree and shrub species from conservation department bundles, including oaks, and a few other oaks from acorns. My favorites are white oaks as well.

    I planted a handful of bur oak acorns a few years ago, and have two small trees as a result. I won’t be around to see how beautiful they could become, but it’s fun to imagine them. Conversely, I had to cut down a few dead oaks this weekend. They died over the the past few years to drought and disease, and although one didn’t look that old- I counted over 180 rings on the stump. The stories they could tell…

    • Thanks, Beau. Oak leaves are amazing when they first begin to expand.

      I almost included bur oak – another of highly fire-adapted species with it’s thick, corky bark – in my short list as well, its sheer massiveness and those burly acorns are so unique. I posted a photo of a nice lone specimen atop a hill in The Loess Hills in Missouri.

  4. Beautiful…it’s not easy to write a love song to gnarly little trees like blackjacks and post oaks. I cherish the attention you give to the underdogs, to beetles, to glades, to all the biota that make Missouri so remarkable place that I can’t pick up and move to Oregon, despite the savannas that are there waiting for restoration.


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