Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Perseus.
frondōsus (anciently also frund-), a, um, adj. [1. frons], full of leaves, leafy: omne sonabat Arbustum fremitu silvaï frondosaï, Enn. ap. Macr. S. 6, 2 (id. Ann. v. 197 Vahl.); so, montes, Varr. R. R. 2, 5, 11: vertex (collis), Verg. A. 8, 351: ramus, Ov. M. 8, 410: vitis, Verg. E. 2, 70: aestas, id. G. 3, 296: taxus frondosior, Sil. 13, 596.