The interest and availability of cypripedium (Slipper) orchids has rocketed during the past 10 years since increasing numbers of plants became available. Prior to 2000 many of the cypripediums offered for sale were wild dug and often did not survive thus giving the genus a bad reputation.
A few growers began raising both species and hybrids from seed thus creating opportunities for enthusiasts to start to grow these orchids successfully.
Much confusing information has been written about how to grow them but it is now agreed that in the UK they are best grown in a mix that is mainly inorganic. My prefered mix is coarse perlite, punice and a small amount of fine bark. In addition I add a small quantity of dolomitic limestone dust to maintain a pH of 6.5 to 7. Avoid planting direct into the ground as plants do not tend to survive for more than a year or two.
They are a typical perennial rhizomatous species that readily bulk up each year provided they are fed regularly (every 10/14 days). Plants should be grown in pots which can either be plunged into the soil or kept as a pot plant. The majority need to grow in semi-shade and in a cool place at all times. They prefer to be frozen at some stage during the winter. They also need to be kept cool during the mid summer as some species and hybrids are prone to crown rot if they get hot, wet and there is too much organic matter in the compost. This tends to breakdown causing acidic conditions.
I use pots of 3 to 5 lt in size for my show stock which means they do not need repotting for 4 or 5 years.
Dormant plants are sent out potted in a mix with very little organic matter. This mix has proved very effective in the efforts to grow quality cypripediums in the UK. On receipt plants should be kept damp throughout the winter and in as cold a place as possible. If they are received in March I would recommend a good watering. This is particularly important if you purchase at a big show as they tend to dry out in the atmosphere of a large hall. Plants kept in any warmth will start growing far too early and suffer in the spring. If purchases are to be planted out then this is possible provided the soil is not frozen. As indicated in the rhizomes should be planted in the pots they are received in to avoid contaminating the mix with soil. It is also sensible to put a copper ring around the pot to protect it from slugs in the spring.
If the plants are to be kept in the pot then the pots can be kept in the garden or a cold frame or in the bottom of a cold greenhouse. Do not let the compost dry out even in the winter as this stresses the plants.
Plants purchased in the spring will have come from my sheltered shade area so will be quite hardy. At a major show however they may have been in a building for several days. These I would suggest should be hardened off in a shady cold frame or against the side of a house before being planted out.