[1] Eucommia jeffersonensis is known only from a single fossil, the holotype, specimen UF 11053, which is housed in the paleobotanical collections of the Florida Museum of Natural History.

[1] The specific epithet jeffersonensis was chosen as a reference to Jefferson County, Oregon where the Gray Butte Flora outcrops and the species type locality is.

[1] The incomplete fruit of E. jeffersonensis is 12.7 millimetres (0.50 in) long when the missing tip area and stipe are excluded.

The structure of the fruit tip is uncertain due to the incomplete nature of the fossil but it appears to have been pointed in general shape.

As with other Eucommia species, the fruit is a samara composed of two flattened nutlets, termed carpels, with a narrow surrounding wing.