Quercus gulielmi-treleasei C.H.Mull

Quercus gulielmi-treleasei was introduced to cultivation by the stalwart collectors and growers of Central American oaks, Francisco Garin and Michel Duhart. It was collected at 2000 m in Santa María de Dota, Costa Rica, in 2007. At Arboretum Chocha, France, it was a compact, narrow tree of about 15 m tall in 2019, while at Iturraran Botanical Garden, Spain, it had reached about 10 m (pers. obs. AJC). They also collected seed from a plant identified as Q. benthamii at 2200 m in San Gerardo de Dota, Costa Rica, in 2001. However, plants from this seed do not appear to be this species, as the leaves are too large with too many veins and the petiole is too short, resembling the short, winged petiole of Q. guilielmi-treleasei, to which they appear closer. One of these plants at Iturraran Botanical Garden was about 10 m tall in 2019 (pers. obs. AJC). Trees from this collection are also at Arboretum Chocha.

For A.E. Murray (1983), this was a variety (or subspecies) of Q. seemannii. Murray made a habit of publishing new combinations, 33 in Quercus alone. They are all treated as synonyms.

This species was first recognised as distinct by Trelease, who annotated specimens as Q. chiriquina, after Prov. Chiriqui, Panama, where the type was collected, but did not publish the name. Muller (1942) did not want to publish a name with this epithet as he thought it could be confused with Q. chiriquiensis, another unpublished name with which specimens of the related Q. seemannii had been annotated. Muller named it after William Trelease, using a Latinization of his first name. William, via the German and Dutch version Wilhelm, was Latinized in the Middle Ages as Wilhelmus, but also as Guilielmus and Gulielmus (Behind the Name 2025).