Native Tree of the Week: Post Oak (Quercus stellata)September 27th, 2012 at 5:00 pm by Chad Evans under Chad's WLFI Weather Blog
Native Tree of the Week last week: Shingle Oak (Quercus imbricaria)
If Bur Oak is the tree of the black loam prairies & savannas in northern Indiana & Black Oak is the tree of the sandy prairies & savannas in northern Indiana, then Post Oak is the tree of the gray prairies & barrens of southwestern Indiana. It is certainly a more southern oak in the U.S. with large amounts of Post Oak on the Blackland prairies of Texas & Oklahoma. It is frequent in the southern U.S. pine barrens & in the Karst barrens/prairie region of Kentucky & Tennessee. It cannot not thrive in a closed, crowded forest situation & survived in either a regime of fire or on really poor, dry sites where other trees cannot crowd it. Where it is found on the richer soils of southwest Indiana, it was historically maintained by fire.
An isolated native population of Post Oak exists on the sandy/gravel slopes near Wea Creek in Tippecanoe County. The closest population outside of this is in northern Clay County, Indiana near Route 159 & 246 intersection (a good 85 miles to the south), where I found several individuals growing mixed with White, Shingle & Black oaks, as well as Shagbark & Mockernut hickories. Open woodland was on an upland slope of thick silty loess overlaying Illinois glacial till. Native vegetation of this area was prairie mixed with barrens & ribbons of timber. It was south of the large prairies running from Prairie Creek & Prairieton, Indiana to Blackhawk, Lewis & Clay City, Indiana.
This Tippecanoe population is an outlier from a much warmer, drier time in Indiana when Post Oak’s range greatly expanded to northern & central Indiana, before being crowded out & dying out by cooler, moister times in the climate pendulum. Like a tidal pool, southern & western species’ ranges shrunk with the wetter regime & the island of more southern & western species remained along the sandy & gravelly areas around Granville. This Post oak population may date back to Medieval times, perhaps the Hypsithermal.
There are really three types of Post Oak in Indiana that may be vague subspecies.
One grows on the gray prairies/barrens region of southwest Indiana on the silty loess soils & clay-loam soils of the region (Western Illinoian Till Plain). In far southern & southwestern Indiana, it grows on clay soils of the Driftless area on acidic flatwoods, often on soils with a fragipan or a hard pan layer restricting downward movement of water. It also grows in Black oak woods with hickory on dry, upland, south-facing slopes of the Driftless area. It grows on higher flatwoods on the old lake plains (lacustrine soils), clay soils of southern Indiana, too. These lake plains are layers & layers of silt & clay from trapped glacial meltwater settling in this part of the state during the Pleistocene.
In pre-settlement barrens areas of Spencer & Warrick County (nature area to view this environment: Bloomfield Barrens Nature Preserve), the Post Oak grows on those clay flatwoods that are acidic & have a fragipan or pan in the soil that restricts downward movement of water. They are wet in spring & bone-dry, desert environments in summer & fall.
Often a southern barrens & prairie indicator species, Post Oak is found with red cedar, blackjack, black oak in rocky glades on high, south-facing slopes in south-central Indiana hill country. I also grows with Chestnut Oak & Virginia Pine in the “knobs” area of far southern Indiana on rocky slopes. Post Oak is found on the Mitchell Karst Plain in former barrens & prairie areas with Black, White & Blackjack Oak & hickories from Orange through Washington & Harrison County, Indiana.
Closest associates to Post Oak in this area: Swamp White Oak (Quercus bicolor); Shingle Oak (Quercus imbricaria); White Oak (Quercus alba); Black Oak (Quercus velutina); Shagbark Hickory (Carya ovata); Mockernut Hickory (Carya tomentosa)
Post Oak Woodland Survey
Odon City Park, Odon Indiana (~40 miles southwest of Bloomington) on rich dark brown loess soil on nearly-flat Illinoian Till Plain with coal-black soil of alluvium running through park. Park was never cut & many oaks are +180 years old with fire-scarring in ring data. One tree in a neighborhood 1/2 mile northeast of the park is over 200 years old with land survey reading “prairie”.
At European settlement this park was surrounded on three sides by tallgrass prairie & the park itself was oak-hickory barrens in land survey with Black Walnuts & American Elm along a stream.
Species Order of Occurrence In the Tract
1. Shagbark Hickory (Carya ovata)
2. Post Oak (Quercus stellata)
3. Mockernut Hickory (Carya tomentosa)
4. Shingle Oak (Quercus imbricaria)
4. Black Tupelo (Nyssa sylvatica)
5. Shumard Oak (Quercus shumardii)
6. White Oak (Quercus alba)
7. Black Oak (Quercus velutina)
8. Pignut Hickory (Carya ovalis)
9. Black Walnut (Juglans nigra)
POST OAK TYPE #2: POPULATION A NORTHERN PROTRUSION CLOSELY-RELATED TO DELTA POST OAK (A SUBSPECIES THAT IS LARGER, MORE VIGOROUS & GROWS WITH OTHER HARDWOODS IN THE HIGH BOTTOMS OF THE MISSISSIPPI RIVER VALLEY) IN FAR, FAR SOUTHWEST INDIANA
There is a different genotype of Post Oak that grows faster, gets larger & is better able to compete with other oaks Posey & Vanderburgh counties in Indiana. I competes with the Southern Red Oak, Cherrybark Oak, Pin, Swamp White, White Oaks in flatwoods of this area well & gets to be a very large tree up to 100′. This genotype is more closely-related to a subspecies of Post Oak called Delta Post Oak. In fact, this population may be a northernmost protrusion of Delta Post that has naturally hybridized with the typical southwest Indiana Post Oak.
Closest associates to Post Oak in this area: Winged Elm (Ulmus alata): Southern Red Oak (Quercus falcata); Cherrybark Oak (Quercus pagodafolia) Swamp White Oak (Quercus bicolor); Shingle Oak (Quercus imbricaria); White Oak (Quercus alba); Black Oak (Quercus velutina); Blackjack Oak (Quercus marilandica); Shagbark Hickory (Carya ovata); Mockernut Hickory (Carya tomentosa); Shellbark Hickory (Carya laciniosa)
POST OAK TYPE #3: MORE RELATED TO SAND POST OAK (GROWS ON DRY EOLIAN SAND HILLS OF LOWER WABASH & WHITE RIVER VALLEYS IN SOUTHWESTERN INDIANA)
There is a type of Post Oak that is restricted to the sand hills of southwestern Indiana. It tends to be shorter & squatty compared to the gray prairie Post Oak & will not grow in loam or clay soil well at all. I grows in the very well-drained Eolian sands bordering the east side of the Lower Wabash & White River Valleys. I have tried to plant Post Oak growing on sand with Post Oak growing on gray prairie or loess soil & the tree never survives. The sand barrens Post Oak genotype is different than the Post Oak of the gray prairies. It is more related to the subspecies of Post Oak called Sand Post Oak, which is not found in Indiana.
Closest associates to Post Oak in this area: Blackjack Oak (Quercus marilandica); Black Oak (Quercus velutina); White Oak (Quercus alba); Chinkapin Oak (Quercus muhlenbergii); Sand Hickory (Carya pallida); Arkansas Black Hickory (Carya texana var. arkansana);
Post Oak is generally a slow grower. In acorns I germinated from a Post Oak woods on an old prairie 40 miles northeast of Vincennes, Indiana, the trees are just above my waste (I am 6’3″)& I germinated them in 2001. The same redbud trees I germinated are over my head now. A tuliptree I planted at the same time & was 1′ tall, is 20′ tall at the same site! I just keep thinking I really won’t see this Post Oaks do much until I am 60 or 70 years old! Truly, it takes a lifetime from seedling to even start to see Post Oak tree really develop.
It is like Shingle Oak in that it cannot tolerate shade & needs warm, open areas to germinate. It cannot compete with most other species well. The genotype more closely related to Delta Post Oak is much better at competition & some shade than the other genotypes. When Post Oak reaches 150-200 years old, though, it is a magnificent tree & still ranks as one of my favorites. I have seen 200-300 year-old Post Oaks in the open that resemble the idyllic very old English Oaks of the British countryside.
Its bark resembles White Oak to sometimes Swamp White Oak, its old limbs are often contorted, twisted & picturesque. It hold its dry, rusty foliage into the winter, especially on younger trees & lower limbs.
Tolerating fire as good as Bur Oak, it sprouts well after a burn & was a main species with Black Oak in the “oak stool” environment of the Karst prairie & barrens in far south-central Indiana at European settlement. Each fire burning over the Post Oak would initiate healing of burned, thick bark, causing large chunks of tissue to form above & just below ground. These reportedly made plowing the virgin reddish Karst soil difficult as these oak stool would break steel plows. This would form thickets & shrubbery of Post Oak.
Being a slow-grower, Post Oak puts a lot of energy into growing deep roots (specifically tap root when young) & put dense, dense rings into the wood. The wood is very heavy & resistant to rot.
Post Oak barrens/savannas:
Leaves, acorns, bark, shape & early fall color of Post Oak: