Lewis & Short

tĕnĕresco, ĕre, v. inch. n. [tener], to grow soft or tender (post-Aug., but tenerasco with Lucr.): in tantum tenerescere acinos, ut rumpantur, Plin. 17, 22, 35, § 189; 28, 12, 50, § 183; Cels. 6, 6, 4; Tert. Res. Carn. 22.