Planting Cypripediums: Volume 2

This second of three volumes is on soil mixes and hardiness for individual species and hybrids.

The most common Cyp. species are C. acaule, C. calceolus, C. formosanum, C. kentuckiense, C. macranthos, C. montanum, C. parviflorum, C. reginae, and C. tibeticum. The most common hybrids are C. Aki, C. Emil, C. Gisela, C. Hank Small, C. Inge, C. Ingrid, C. Maria, C. Michael, C. Philip, and C. Ulla Silkens. Hybrids grow pretty much the same; species have individual needs.

C. acaule requires a very acidic soil, pH 3.5-5. I recommend spreading the roots over sand and covering in pine mulch, then watering sparingly with a solution of pure water and vinegar, at a rate of 1 ounce vinegar per gallon water. Hardy to zone 2.

C. calceolus should not be confused with our native yellow lady's slipper (C. parviflorum). I am referring to the European clone. A pH of 7-8 is necessary, with perfectly-drained soil. Use a balanced mix with loam, sand and gravel. Hardy to zone 3.

C. formosanum makes a great potted plant if it isn't hardy to your region. Known as an easy species, it prefers a pH of 6-7, in a well-drained soil. Always add drainage material in the bottom in the pot. Hardy to zone 6.

C. kentuckiense is just beginning to gain popularity. It is sought-after for its large flowers (largest in the genus). It likes a sandy soil with a pH of 5-6. I recommend using mostly sand with a little loam and a top-dressing of conifer mulch. Hardy to zone 3.

C. macranthos is very popular for its showy flowers in shades of pink, purple and red. It must have a prefectly-drained soil; use a well-balanced mix with loam, sand and gravel; pH around 7. Hardy to zone 2.

C. montanum is sought-after by collectors but has a reputation of being difficult to grow. It must have a sharply drained soil with plenty of gravel and sand, pH 7-8. I recommend planting on a slope. Hardy to zone 2.

C. parviflorum is the most common Cyp. It is easy to grow in a well-drained soil, pH 6-7. Hardy to zone 2.

C. reginae is the most majestic of the Cyps and is highly sought-after. It is relatively easy to grow in a well-drained soil, pH 7-8. Likes lots of moisture (NEVER wet!) and fertilizer. Hardy to zone 3.

C. tibeticum is a collector's species that is closely allied to C. macranthos but has darker maroon flowers. It requires perfect drainage, pH around 7. I'm unsure about hardiness but it has been grown in zone 3.

All hybrids like well-drained soil and lots of fertilizer, pH around 7. They're all hardy to at least zone 3.

The third and final volume will be about care after planting.