Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
arbŏrĕus (arbŏrĭus, Varr. L. L. 5, § 137 Müll.), a, um, adj. [arbor], of or pertaining to a tree: frondes arboreae, Ov. M. 1, 632; 4, 637: radix, id. ib. 8, 379: umbra, id. ib. 10, 129: fetus = poma, id. ib. 4, 125; 10, 665; 13, 820; 14, 625; 15, 97: fetus, Verg. G. 1, 55; Col. poët. 10, 401: fruges, Cornif. ap. Serv. ad Verg. G. 1, 55: coma, tresses, locks, i. e. leaves, = frondes, Prop. 3, 14, 28: comae, Ov. Am. 2, 16, 36: frondes, id. ib. 3, 5, 7: folia, Plin. 21, 15, 51, § 87: cornua cervorum, branching, Verg. A. 1, 190: telum coruscat, Ingens, arboreum, huge, like a tree, id. ib. 12, 888: Harundini Indicae (est) arborea amplitudo, attains the size of a tree, Plin. 16, 36, 65, § 162.