Orchid seeds are extremely small and have limited nutrient reserves. In nature, the germination and seedling development of all orchids are dependent on the establishment of mycorrhiza. Orchid mycorrhiza differ from other types of mycorrhiza in the fact that the nutrient flow is one-sided from fungus to orchid . Orchid mycorrhizal fungi differ from most other mycorrhizal fungi by being of basal parasitic or saprophytic nature, most orchid endophytes are referred to the form genus Rhizotonia s.l. At germination the fungus infects the germinating seed either through the suspensor or through the rhizoids and forms hyphal coils (pelotons) in the host cells, the pelotons are eventually digested by the orchid , thus supplying the necessary energy for germination.
Orchid seeds may however be germinated in pure aseptic culture in vitro on media containing minerals and sugars. However, this method, known as the asymbiotic method, is only suitable for a limited number of species, mainly tropical epiphytes.
Three major methods for in vitro propagation of orchids exist: symbiotic seed propagation, asymbiotic (or aseptic) seed propagation and tissue culture. These methods each have advantages and limitations: symbiotic seed propagation is the only method suitable for a number of temperate terrestrial orchids