Quercus × exacta Trel.

Engelmann found this hybrid west of St Louis, Missouri, a few years before 1877. It was fruiting, and he mentioned that it was propagated by Mr Meehan of Germanstown, Pennsylvania. The offspring were said to be ‘completely agreeing in character with the parent.’ Of three trees at the Arnold Arboretum, two trees received in 1889 from Thomas Meehan & Son and were 91.3 cm dbh in 2015 and 67 cm dbh in 2017. Another, received as seed in 1931, perhaps from one of the older trees, was 64.1 cm dbh in 2017 (Arnold Arboretum 2025). A tree supplied by Thomas Meehan & Son was an impressive part of the oak collection at the New York Botanical Gardens (pers. obs. RC 2014), but it had died by 2022 (Forrest 2023).

A tree at Aboretum du Passadou, France, was acquired in 1997 from Arboretum national des Barres, and according to Jean-Louis Hélardot, (pers. comm. 2025) is a very beautiful tree that has grown quickly and fruited copiously after 15 years; he notes that the seedlings faithfully reproduce their parent, which coincides with Engelmann’s observation.

Trelease published the name in 1917, but provided no other information aside from the hybrid formula. The derivation of the name is not clear, but may refer to Engelmann’s remark that the seedlings obtained from the tree he found were exactly the same as the parent (i.e., ‘completely agreed in character’). The epithet derives from Latin exactus (‘exact, accurate’ by extension from ‘determined, found out, ascertained’) (Wiktionary 2025).