Svante Malmgren Henric Nyström
Platanthera, Coeloglossum and Nigritella
are some genera quite closely related to Dactylorhiza and Gymnadenia
and most of them respond to similar methods of large-scale asymbiotic
propagation as Dactylorhiza.
Platanthera is easily propagated on sterile media and is grown like Dactylorhiza.
Medium: Standard + potato + pine-apple, like Dactylorhiza.
Seed treatment:The seed coat is very thick, but by using H2SO4 + NaClO plus a cool treatment after sowing, just like Gymnadenia, a 20-50% germination rate can be achieved. Sowing half-mature seed gives even better results.
Young plants grow healthily on soil but they take 5 years to reach flowering size. Platanthera bifolia, however, probably has the most wonderful scent of all our native plants, so the wait is worthwhile!
As a matter of interest, it is worth mentioning that Svante Malmgren on one occasion obtained seed of Platanthera oligantha for scientific research. This might be Europe’s rarest orchid. Germination and growth on medium were not problematic, but transferral to soil failed. This could be because of difficulty matching the species’ temperature requirements. New attempts would overcome this problem in all likelihood.
(This illustrates that the key to successful hardy orchid propagation is to follow the natural growth cycle of each species over the year and to provide the necessary sequences of temperature change.)
Neottianthe cucullata is another rare little orchid from eastern Europe. Seeds were sown twice. Germination and growth on medium were excellent and transferral to soil posed no problems the first time, but failed another year. A shortage of seed, though, has prevented further propagation.
Nigritella nigra of Swedish origin (the plant is triploid and apomictic) has been raised for many years for a conservation project in northern Sweden. Propagated like Dactylorhiza, but seem to benefit and grow bigger and safer if kept two years on medium, producing new, bigger tubers second year. Also germinates a little better if kept cool after sowing, but otherwise it is very easy to propagate on medium but is a little sensitive when transferred to soil, mainly because of the problems of maintaining suitable temperature conditions. First year seedlings are small and seem to prefer a cool mountain climate. For this reason, Nigritella is not a good plant for the garden! Don´t buy from the Internet! They are rarely propagated from seed!
On a few occasions, seed of central European Nigritella has been sown and grown on sterile media. It seems to behave similarly to the Swedish plants.
Leucorchis albida (there are two Swedish subspecies) is now greatly threatened with extinction outside mountain areas. It may already be extinct in Denmark. Attempts to propagate it for a conservation project in Sweden have just begun.