Try to make your search as simple as possible:
Gelsemium will find all items including that sequence of letters.
Search results for "Gelsemium":
"Gelsemium garrocha" - Tecoma fulva ssp. garrocha
"Gelsemium nitidum" - Gelsemium sempervirens
"Gelsemium sambucifolia" - Tecoma stans v. sambucifolia