From the Greek trachelos — a neck, sperma — seed, alluding to the form of the seeds.
Twiners or lianas, evergreen; latex white. Stems woody, without spines, sometimes stoloniferous. Leaves opposite, stalked; blade well developed; colleters absent at base. Inflorescence terminal or axillary, cymose. Flowers sweetly scented, stalked. Corolla salver-shaped; tube cylindrical; lobes convolute in bud, overlapping to the left. Corolline corona absent. Stamens enclosed or protruding, attached midway in tube, converging around and sticking to style head. Disk annular or of 5 oblong glands. Fruit of separate carpels, a pair of follicles, dehiscent along adaxial suture. Seeds numerous, linear, not winged, comose at micropylar end.
Two species and cultivars are commonly cultivated. Tolerant of mild frosts.
Cuttings or seeds.
Twiners or lianas, corolla salver-shaped with lobes overlapping to the left in bud, disk annular or of 5 oblong lobes.
About 10 species in E Asia and N America.
Source: (2002). Apocynaceae. In: . Horticultural Flora of South-eastern Australia. Volume 4. Flowering plants. Dicotyledons. Part 3. The identification of garden and cultivated plants. University of New South Wales Press.