If you hike in the woods, especially in eastern North America this month, you're likely to see lady's slipper (Cypripedium) in bloom. If you want to add these plants to your garden, now is the time to order plants for delivery at planting time.
All native species of lady's slipper orchids have long been popular plants for naturalistic gardens and greenhouse collections. But like many natives, their beauty has been their downfall. For years, gardeners have dug wild plants for their gardens, only to have the transplanted specimens fail. Add to this the loss of natural habitats to urbanization, and you can see why lady's slippers are now officially endangered in many areas.
Now available from one nursery, Raising Rarities of Jacksonville, Vermont, are 3- to 5-year-old blooming-size plants of four Cypripedium species. The plants are expensive, but they're more likely to survive than 1-year-old seedlings available from other nurseries.
Raising Rarities offers four of the native lady's slippers as large, blooming plants: showy lady's slipper, C. reginae; large yellow lady's slipper (C. parviflorum pubescens); small yellow lady's slipper (C. parviflorum parviflorum); and the rare Kentucky lady's slipper (C. kentuckiense), which has a creamy-white pouch and mahogany petals. Kentucky lady's slipper is larger, and at $100, much more expensive; bare-root plants of the other kinds cost $35. Despite hardiness zones listed in some references, all kinds are hardy to zone 3.
Raising Rarities ships plants twice a year: in April after the soil has thawed but before growth resumes, and in September and October after a hard freeze but before snow.
Plant the dormant rhizomes with bud tips upright in a spot with open shade, good air circulation, and moist, well-drained soil that has a neutral pH. Amend the planting area with equal quantities of perlite and leaf mold. Use more perlite and leaf mold if you have clay soil. Cover the rhizome with 1/4 inch of loose soil and keep the area moist. Fertilize with an all-purpose, liquid plant food at one-quarter strength once growth begins and then every two weeks until flowering. Cover plants during winter with a 6-inch layer of chopped leaves to prevent soil heaving.