Lewis & Short

silvesco (sylv-), ĕre,

  1. I. v. inch. n. [id.], of the grape-vine, to grow or run wild, to run to wood: (vitis) ne silvescat sarmentis, Cic. Sen. 15, 52: nec pati vitem silvescere, Col. 4, 11, 2.
  2. II. Transf.: capilli silvescentium crinium velleribus involuti, Arn. 3, p. 109.