I have been growing lady slipper orchids, genus Cypripedium (here after called Cyps), in a warm temperate climate for 7 years in southern Japan (latitude 34 N). In the spring, when the plants are emerging and flowering, I get a jolt of shear joy – mission accomplished. Then, in June, the monsoon rains kick in and the rotting begins. Bugs get more active and slugs are a constant threat.
By late July (as I write this), I am positively sure that all is lost for the season since just about everything is worn, torn, ripped, rotted or eaten. The oven heat of August and September seems to only emphasize the point – growing Cyps in a hot summer climate is madness. Come November, with its cool rains and falling maple leaves, I dare to check the plants and am often surprised with what not only endured, but even grew well that year. The following article is the method I’ve worked out over the years to grow these lovely terrestrial orchids.
First of all, let me explain the climate I’m working with. Kyushu, the southernmost main island of Japan, is a warm temperate climate sitting on the eves of the subtropics. A typical day in January has a high around 7 C (44.5 F) and a low of 2 C (35.6 F), with an daily average around 5 C (41 F). Why spend so much time worrying average temperatures? The reason is simple – to vernalize adequately (have a proper dormancy period), most Cyps require at least 3 months of an average temperature at or below 5 C. My town, situated just on the edge of a mountain range, barely fulfills that requirement. In fact, the average temperature is a bit warm in the winter months.
If winter weren’t trouble enough, June and July create more problems. This is due to the inordinate rainfall of the summer monsoon. A meter or more of it can fall in just 6 weeks, something most Cyps don’t enjoy. In mid July the rains stop and the oven turns on. Average highs are in the low 30s C (90-92 F) with lows only down to the upper 20s C (80-82 F). Fall comes late, with October drying off and slowly cooling off, but the true colder nights don’t come until late November or early December.