The Collaborative International Dictionary of English v.0.48:

Petaled \Pet"aled\ (p[e^]t"ald), a. (Bot.)
   Having petals; as, a petaled flower; -- opposed to
   apetalous, and much used in compounds; as, one-petaled,
   three-petaled, etc.
   [1913 Webster]

WordNet (r) 3.0 (2006):

petaled
    adj 1: (of flowers) having petals [syn: petalous, petaled,
           petalled] [ant: apetalous, petalless]