Botanizing at St. Joe State Park

Dry post oak woodland.

This week’s destination for the WGNSS Botany Group outing was St. Joe State Park, where the western portion of the Bicyle/Hiking Trail runs along a prime example of dry post oak woodland. Such woodlands were common in Missouri during pre-settlement times but have been largely eliminated from the present-day landscape due to incompatible land management practices, including fire suppression. Post oak woodlands depend upon periodic fires to maintain an open canopy, allowing a rich ground layer of native grasses and forbs to flourish in the abundant sunlight. In pre-settlement times, this happened naturally as a result of lightning strikes; however, remnant post oak woodlands exist today largely as a result of active landscape management including the use of prescribed burns and selective thinning. Evidence of these practices was easy to find in this remarkably restored example of an original post oak woodland.

Prescribed burns help to maintain an open canopy and a rich herbaceous ground layer.
Selective girdling optimizes species composition while minimizing ground layer disturbance.

At the end of January, there is still a lot of winter left to endure—far too early to be thinking about the still-distant-spring even at our “middlin’ latitudes.” Nevertheless, even at this early date, the buds of Ulmus rubra (slippery elm) are noticeably swollen. (I’ve always felt “slippery” was a misnomer for this species. I know it refers to the slippery texture of the inner bark when chewed, but the leaves are rough, and the twigs are rough, and the buds are rough as well—and who even does that [chews the inner bark] anymore?!) It is this roughness to the leaves that most easily distinguishes U. rubra from the similar U. americana (American elm), but during winter it’s fuzzy, rusty-red buds provide the clue instead. If one has a pocketknife, a slice into the bark to look for alternating light/dark layers (the absence of which signifies U. rubra) can also be used.

Ulmus rubra (slippery elm).

The rich ground layer of a post oak woodland dazzles during spring and summer, the temporal sequence of floral displays belying the diversity that produces it. This diversity does not disappear during the winter, nor does the evidence of it—it merely expresses itself in different form. To recognize the plants that are there, one must train their eyes to see these different versions of them. Bright yellow flowers are replaced by dry seed boxes… fleshy green leaves with purple ball inflorescences are replaced by naked stems with dehiscent pods… delicate white petals are replaced by prickly pods. The ability to recognize the elements of a landscape at any moment—not just at their most beautiful—makes it easier to enjoy the landscape itself at any moment. Following are some of the plants we saw, no doubt distinctive when in bloom, but also recognizable when not if one knows what to look for.

Dasistoma macrophylla (mullein foxglove).
Anemone virginiana (tall thimbleweed).
Manfreda virginica (formerly Aloe virginica—false aloe, rattlesnake master, Virginia agave).
Dioscorea villosa (wolf yam).
Asclepias purpurascens (purple milkweed).

During the previous week’s outing at Hawn State Park, the group spent a fair amount of time distinguishing Missouri’s five species of Betulaceae—all of which can be found growing together along the banks of Pickle Creek. One is not likely to see three of them along the margins of a dry post oak woodland, but the two remaining—Corylus americana (American hazelnut) and Ostrya virginiana (American hop hornbeam), both much more tolerant of drier situations—were seen in abundance. These two species also happen to be the two that are most often confused with each other—especially during winter, giving the group another opportunity to study their subtle differences. Both develop male catkins during the winter, but those of C. americana tend to be larger, lighter in color, and frequently occurring singly along the branch. The winter twigs are a bit more distinctive—with tiny hairs and rounded buds in the former, versus hairless with pointed buds in the latter. Of course, of the two, only O. virginiana produces the distinctive hops-like fruits that often persist into the winter, so their presence immediately identifies any plant possessing them.

Corylus americana (American hazelnut) (L) versus Ostrya virginiana (American hophornbeam) (R) – male catkins.
Corylus americana (American hazelnut) (L) versus Ostrya virginiana (American hophornbeam) (R) – winter buds.
Ostrya virginiana (American hophornbeam) (R) – last season’s fruit.

Direct comparisons of winter twigs proves to be a useful identification technique for other similar species pairs—even those in the same genus. Acer saccharum (sugar maple) and A. rubrum (red maple) often grow in close proximity and are similar enough to be frequently confused. When twigs of the two are placed next to each other, however, the differences are apparent. Color alone—A. rubrum usually exhibiting a reddish tinge to the twigs and buds—is not always diagnostic, and both species have what could be called pointed buds. Touch the tips, however—the buds of A. saccharum are sharp enough to prick the finger, while those of A. rubrum are blunted just enough to avoid feeling the prick.

Acer saccharinum (sugar maple) (L) versus Acer rubrum (red maple) (R) – winter buds.

Along the length of the trail, I noted an abundance of dry, persistent flower stalks of Hydrangea arborescens (American hydrangea) colonizing the bordering rock ledges. Normally found in moist (and frequently inaccessible) situations, its presence in a dry post oak woodland suggests drainage through the layers of dolomite underneath the woodland reaches the surface in these exposed toe-slopes, keeping them persistently moist. While the promised floral display in June is reason enough to return, my interest in woodboring beetles provides additional motivation, as its flowers are a favorite of a diverse group of woodboring beetles call flower longhorns (subfamily Lepturinae)—some of which having been associated only with this plant. Time to mark the calendar!

Members of the WGNSS Botany Group (L–R): Keith Woodyard, Eileen & Tom Buescher, Alan Brandt (hidden), John Oliver, Kathy Thiele (hidden), Burt Noll, Michael Laschober, Pete Kozich.

©️ Ted C. MacRae 2022