Seed Propagation and Seedling Production of Temperate Lady’s Slipper Orchids (Cypripedium)

Peter Zale, Longwood Gardens

Despite significant advances in seed propagation and production of lady’s slipper orchids (Cypripedium spp.) in the last 25 years, the genus remains rare in ex situ collections, access to seedlings from local populations that may capture important genetic diversity is rare, they are expensive to purchase, and there are still inconsistencies and difficulties with seed propagation. Over the last six years we worked with at least 13 Cypripedium species represented by 29 seed accessions that resulted in updated information to increase the success and repeatability of propagation efforts.  Hand pollination of flowers is necessary and resulted in viable seeds in all instances where performed.  Experiments have also shown that use of immature seeds harvested at 45 to 52 days after pollination result in the highest rates of the germination on Phytotech labs T839 Cypripedium medium with the addition of 1 cm3 of Russet potato per 20 ml of medium.  Immature seeds of all species were incubated in the dark at room temperature and germinated within 4 to 6 weeks of sowing.  At 90 days after sowing, seedlings began to differentiate and were transferred to T839 medium without potato and incubated in the dark at room temperature where development continues for another 6 to 12 months.  At this point seedlings were deflasked, washed clean, placed in plastic bags with a minimal amount distilled water to prevent dehydration, and placed in the cooler at 36° f to 40° F for 90 days.  After the vernalization period is complete seedlings are potted into a mixture of Kanuma, Akadama, and perlite and placed on greenhouse bench where they produce their first shoot.  Greenhouse/Nursery acclimatization of seedlings is the most difficult part of the propagation process and the most likely stage when seedlings can be lost.  If successful, seedlings can flower three to five years.