monocephalous
/ˌmɒnə(ʊ)ˈsɛfələs/ /ˌmɒnə(ʊ)ˈsɛf(ə)ləs/ /ˌmɒnə(ʊ)ˈkɛfələs/adjective
Of a stem, stalk, etc.: bearing a single capitulum or umbel. Of a plant: having its flowers in a single capitulum or umbel.
Origin
Mid 19th century (in an earlier sense). From mono- + -cephalous, perhaps after French monocéphale.