Scientific Name
Quercus marilandica ‘Blackjack Oak’
Blackjack oak is a member of the red oak group, which is evident in the small bristles at the tips of its otherwise bluntly pointed lobes. The leaf margins are usually more rounded than those of other commonly encountered red oaks. Leaf shape can vary considerably on this species, but most follow a general bell-shaped pattern, with the widest portion and most pronounced lobing toward the outer end. The undersides are covered with a brown pubescence. Fall color can be especially striking, ranging from bright red to orange. The acorns are about 3/4 inch wide and sit in a cup that often has a goblet-like form.
Blackjack oak is native primarily to the southeastern United States but extends into hotter, drier parts of Oklahoma and as far north as the Iowa–Missouri border. That range suggests a good degree of cold hardiness, along with a tolerance for heat and drought that makes it promising for our region. It is also well known for its ability to grow in poor soils where other oaks struggle. This is a relatively small oak, and we do not expect it to exceed about 30 feet in height here.
At 19 feet tall with a trunk diameter of just 4 inches, the Regis specimen is currently, as of 2026, the largest known in Colorado. That distinction likely reflects its rarity as much as its performance, since the species has not received the same attention as larger, more familiar oaks. If it continues to do well, it could find a niche in future urban plantings where a smaller oak is desirable.
Based on leaf variation, there are some signs that this tree may be of hybrid origin. Oaks are well known for hybridizing, especially when grown from seed in areas where related species overlap and open pollination occurs. In this case, a connection to another red oak or possibly a black oak hybrid is plausible. Another blackjack oak in the Regis nursery shows characteristics more typical of the species, and we plan to plant it on campus in the spring of 2026.