Evan,
OK, here it is! A number of years ago, I discovered that changing fert element ratios probably takes place seasonally in natural settings and that these changes cue certain plants to begin storing food for their dormancy periods. Specifically, I was working with Amorphophallus and found that with the proper fert regime used throughout the whole growing season, one could cause the tubers to grow so large that they could distort or break their pots open. The regime is as follows During the first 1/3 of the growing season (leaf emergence is the start), use a fert like 18-6-8, something with nitrogen highest and phosphorus lowest of the three.. During the second 1/3 of growing season (usually midsummer period), switch to something like 14-14-14 (NPK all about equal). Finally, in the last 1/3 of growing season (late summer, early fall), switch again to a high phosphorus mix such as 14-26-6. That is my special secret sauce for maximum tuber size in plants which go dormant for winter. Be sure that adequate levels of micro-nutrients are available all season. Not only will this augment tuber growth, but will encourage blooming and excellent new leaf health on emergence.
LariAnn
Aroidia Research
