Propagation, cultivation and breeding of terrestrial temperate orchids, with focus on Cypripedium spp.

Sammanfattning: Temperate terrestrial orchids have received increased horticultural attention as the new exclusive perennials for the garden. Temperate terrestrial orchid seeds have been found to germinate and develop readily asymbiotically on suitable media in vitro. To achieve a successful germination the water impermeable seed coat must circumvented; either by sterilization in a hypochlorite solution or culture of immature seeds. Further the culture must be kept in darkness until the first leaves appear. Germination and proliferation media for terrestrial orchids should have a low concentration of mineral salts, where the nitrogen is provided in organic form. Soluble sugars as sucrose are also required. Growth promoting effects has been seen with the vitamin B complex and various organic liquids, especially pineapple juice. Kinetin has been found to improve germination and growth in some Cypripedium spp. The optimum temperature for seedling growth in vitro is usually around 20°C. The protocorms developed after germination should be transplanted to new media regularly. Periods of lower temperatures should occur to induce dormancy periods resembling natural conditions. Later plantlets of sufficient size could be planted in soil, and acclimatized to outdoor conditions. Vegetative propagation could be done by dividing protocorms or underground parts. Micropropagation of young tissues is another way, which has not yet been fully explored. The genus Cypripedium consists of 46 species half of which have been explored in breeding new cultivars. Closely related species rather easy produces vigorous hybrids, but there are indications that all species could be crosses. The distribution of the genus is circumboreal, with a wide span of habitats, which provides good breeding material for hardy and adaptable cultivars. Cypripedium cultivars should be planted shallow in a partly shaded site, moist, but yet well drained. The soil should ideally have a high content of organic matter, and be in the slightly acidic pH range.