Why are the seeds of this species difficult? The seeds may have physiological dormancy, which can be overcome by mimicking the seasonal patterns of the species' native habitat.
Heliotropium zeylanicum (Image: S. Wood, RBG Kew)
This species most probably has Orthodox seeds (based on other species in the same genus) - dry to 15-20% eRH and store at -20ºC, or as cool as possible.
Germinate on agar, germination paper (top of paper) or sand, under an alternating temperature regime of 35/20ºC (with an 8/16hr photoperiod). Add gibberellic acid to the germination medium to encorage growth.
The seeds of this species may be Physiologically Dormant (based on other species in the same genus). If germination is low, overcome dormancy by mimicking the seasonal patterns of the species' native habitat. Use a moist pre-chill or pre-heat treatment (depending on local climatic conditions) or a dry after-ripening treatment, before germinating the seeds on agar, germination paper or sand at their optimum temperature. If this does not work, you can perform delicate surgery to enable the embryo to grow. Excise the tissue near the root tip.
(Image: S. Wood, RBG Kew)
The fruits (1.7-2.3 mm x 2.0-2.5 mm) are almost globe-shaped, hairless and wrinkled. The nutlets are free, with convex and irregular inner surfaces.
The fruits are usually bright brown at maturity.
Accepted name: Heliotropium zeylanicum (Burm.f.) Lam.
Synonyms: Heliotropium subulatum (A.DC.) Vatke, Heliotropium zeylanicum var. subulatum (Hochst. ex A.DC.) Chiov., Tournefortia subulata Hochst. ex A.DC., Heliotropium inconspicuum Dinter ex Vaupel, Heliotropium subulatum var. arenarium Vatke, Heliotropium micranthum Welw., Tournefortia stenoraca Klotzsch, Heliotropium curassavicum var. zeylanicum Burm.f.
Common name: heliotrope
- Food and Agriculture Organization of the United Nations and International Plant Genetic Resources Institute (1994). Genebank Standards. FAO/IPGRI, Rome, Italy.
- AFPD (African Flowering Plants Database) - Conservatoire et Jardin Botaniques de la Ville de Genève, Switzerland, and South African National Biodiversity Institute, Pretoria, RSA: Heliotropium zeylanicum.
- Flora Zambesiaca - Royal Botanic Gardens, Kew, UK: Heliotropium zeylanicum.
- PROTAbase (Plant Resources of Tropical Africa) - Wageningen, Netherlands: Heliotropium zeylanicum.
- SID (Seed Information Database) - Royal Botanic Gardens, Kew, UK: Heliotropium zeylanicum.
- Tropicos - Missouri Botanical Garden, USA: Heliotropium zeylanicum.