27 October 2012 – Evidence of Hybridization in Overcup Oak

27 October, 2012 Botany Bill 0 Comments 2 categories

Overhead branches of Overcup Oak

Yesterday, I went out to the location along Millrace Road where I spotted the putative hybrid (Quercus lyrata X Quercus ????). The road serves as the boundary between the North Tract and the Central Tract.

I took an quick inventory of the trees on both sides of the road. The fact that there was a large number of acorns underneath the individual trees and the trees were mostly separated made it fairly easy to guess which acorns came from which tree.

Acorns from putative hybrid

There were two types of acorns and I used this to differentiate the trees into two groups. One with cups which mostly covered the nuts, and the other with cups which covered about one half of the nuts. Additionally, the margin of the cups were ragged in comparison to the margins of the former group. The former keys out to Quercus lyrata, and the latter has a strong Quercus lyrata strain with possibly characteristics of another species in the white oak group (Quercus).

There were several trees of the first group on the Central Tract on the south side of the road. I was able to collect a large number of acorns. However, even with my tree loppers, I was unable to get a branch with twigs, buds, and leaves because they were too high up the trees. I collected a handful of leaves which could have come from these trees.

Leaf from putative hybrid

For the second group, there was one tree next to the road on the Central Tract side and a couple in a swampy area about 10 feet away from the road on the North Tract side. I `also collected several acorns underneath these trees. These acorns were smaller and as noted above, the cups were markedly different. I was able to collect some leaves, twigs and buds from a lower hanging branch on one of the trees on the North Tract side.

Oaks from the white oak group, Swamp Chestnut Oak (Quercus michauxii) and White Oak (Quercus alba) were spotted nearby. It is possible that one of these two is the other parent for this putative hybrid. Another species Swamp White Oak (Quercus bicolor) is another possible parent, but no specimens were found nearby.