Flora of North America species comparison

Quercus robur is one of the oaks most commonly cultivated in temperate and subtropical parts of the world. In North America it is most commonly seen in the eastern and northwestern parts of the United States and and in southeastern and southwestern Canada, where it tolerates a wide array of conditions and is extremely hardy. In Washington, New Brunswick, and Nova Scotia, apparently reproducing populations persist in the wild. Elsewhere, although actual naturalization appears to be rare, Q. robur should be expected to persist around old homesites and other places of cultivation.

Quercus robur most closely resembles our native species Q. alba in leaf form. In contrast with Q. alba, which has relatively long petioles (longer than 10 mm), acute leaf bases, and subsessile fruit (rarely on peduncles to 25 mm), Q. robur is easily distinguished by its shorter petioles (less than 10 mm), cordate, almost clasping, leaf bases, and fruit on long (more than 35 mm), thin peduncles.

Quercus robur is one of the oaks most widely celebrated in literature; it has wood of exceptionally high quality for the manufacture of furniture, and it previously was the most important wood used in the manufacture of wooden sailing vessels in Europe.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Quercus virginiana is one of the commonest and best known species in the coastal region of the southeastern United States. In the past, it was widely used for structural pieces in the manufacture of wooden ships, and large groves were actually considered a strategic resource by the federal government. Historically oil pressed from the acorns was utilized. Like other members of the live oak group (Q. minima, Q. geminata, and Q. fusiformis), Q. virginiana seedlings form swollen hypocotyls that may develop into large, starchy, underground tubers. In the past, the tubers were gathered, sliced, and fried like potatoes for human consumption. The tendency for the tree members of this group to produce rhizomatous growth and clonal shrubs in juvenile stages, and in response to damage, fire, and poor soil conditions, has led to considerable confusion in delimiting the species. This is exacerbated by considerable plasticity in leaf form. When evaluating specimens an effort should be made to sample broadly within a population. The tuberous condition mentioned above suggests that live oaks have different phases in their life history that may persist depending on the environmental conditions. This is not uncommon in other woody plants that occur in seasonally dry, fire-prone habitats of the southeastern United States.

The Houma used Quercus virginiana medicinally for healing dysentery (D. E. Moerman 1986).

Putative hybrids between Quercus virginiana and Q. minima are known, but care should be taken to avoid assigning hybrid status to clonal phases of Q. virginiana solely on the basis of habit. Hybrids with Q. fusiformis and Q. geminata are discussed under those species. Occasional putative hybrids with Q. stellata are also found, and those tend to be semi-evergreen with shallowly lobed leaves.

Some named putative hybrids are: Q. ×burnetensis Little (= Q. macrocarpa × Q. virginiana); Q. ×comptonae Sargent (= Q. lyrata × Q. virginiana); and the artificially produced hybrid, Q. ×nessiana E. J. Palmer (= Q. bicolor × Q. virginiana).

(Discussion copyrighted by Flora of North America; reprinted with permission.)