Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
* mātresco, ĕre, v. inch. n. [id.], to become a mother, to become like one’s mother (ante-class.): utinam nunc matrescam ingenio, Pac. ap. Non. 137, 7 dub. (Trag. Rel. v. 139 Rib., maturescam): matrescere, μητράζειν, Onomast. Vet.