Blackjack and Post Oak
The Scrub Oak complex in the midwest is made up primarily of post, blackjack, and to some extent small white oaks. These trees are smaller in stature due to the harser environments in which they are found. In the quest for smaller trees for planting under powerlines and in difficult urban situations, the scrub oaks may be good candidates. Post Oak has been used successfully in Texas. In southern Ohio, post and blackjack oak have been shown to be tolerant of acid damaged soils, and limited topsoil. Availability in cooler zones is limited and more urban testing is definitely needed.
Blackjack Oak (Quercus marilandica
This tree in the red oak group is called "scrub oak" by some referring to the smaller stature that can be an asset in the urban environment. Blackjack as a common name refers to the oblong or wedge shaped leaf that is variably three lobed and widest near the tip of the leaf. The leaf is deep green and glossy on top and rusty pubescent beneath. The foliage is quite drought resistant. Fall color is russet and not showy. The tree tolerates some notably poor soils.
This tree is a common pioneer invader in Virginia. Flood plain species and pioneer invaders have proven to be some of the most urban tolerant trees we use. In Ohio, blackjack oak is rare but occurs in the unglaciated area of the state in southern areas of zone 5 and in zone 6. It is likely to be found in an old field especially if the area is dry and impoverished. The twiggy growth and dwarf habit makes the blackjack oak a poor timber tree but offers advantages in the restricted space found in our cities. It typically occurs in zones 6 and higher, but there are significant populations in southern Michigan which could provide a seed source if needed.
Post Oak (Quercus lyrata)
This is a white oak with smaller than average stature. The lobed foliage is dark green and attractive especially during mid summer. Insects and disease problems are reasonably minor. Cold-hardiness is not a problem. As with all the white oaks, the wound response is good. The young plant has a regular outline with closely spaced branches. This tree is native in the acid soil regions of Ohio and may be less adaptable to alkaline soil than the chinquapin or bur oak.
This tree is widely used in the urban centers of Texas. Post oak has a very regular outline and excellent urban tolerance. Restricted root space is well tolerated and is often a site characteristic where the tree is native in Ohio. Where space is a concern, this is an excellent choice.