Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
quernus, a, um, adj. [quercus; cf. querneus], of oaks, oaken, oak- (poet.): quernas glandes tum stringere tempus, Verg. G. 1, 305: vimen, id. A. 11, 65: stipes, Ov. F. 4, 333: corona, a garland of oak-leaves, id. Tr. 3, 1, 36.