1Having passed beyond the state of maturity; beginning to age or deteriorate.
Of a tree: having reached a developmental stage at which growth has slowed down or virtually ceased, or at which the tree has begun to lose commercial value as timber.
overmature/ˌəʊvəməˈtʃʊə/ /ˌəʊvəməˈtjʊə/ /ˌəʊvəməˈtʃɔː/
Late 19th century; earliest use found in American Naturalist. From over- + mature.