From the literature, it is seen that when the canopy of elephant foot yam turns yellow and withers away, the yam is ready for harvesting. But my friend, who has been cultivating elephant foot yam for the last several years says that if you dig up the yam immediately after the canopy has withered away, you will get only a small yam. He says that you should allow two more months to the tuber, when it will become bigger. I cannot understand how the yam will become bigger without the photo-synthesizing canopy. But he was insistent about it.
Thinking about it further, we see that a yam with withered canopy, if left in the ground, will sprout shoots in April to May some time before the monsoons. In Kerala, the traditional knowledge is that the yam setts of 750gm to 1 kg are planted in the month of Kumbha (Phalgun, Feb-March) on the day of the full moon (and the yam will grow to be as big as the full moon!). The sprouts will appear in Apr May. This means that the underground tuber undergoes a change independent of canopy or photo-synthesis. So it is possible that the the yam that has stored certain material (starch and others) before the canopy withers away, could continue to process those initial material and transform them into a more voluminous and tasty (for humans) form silently under ground without any help from the canopy, leaves and photo-synthesis. This could be the plant equivalent of the rumination technology followed by the cows. That is, create a first set of chemicals using photo-synthesis (quickly eat the grass, mix it with saliva and process it in the first 2 chambers of the stomach), store them in a small tuber in a concentrated form, shed the canopy and then quietly work underground transforming the concentrated material to a voluminous form (regurgitate and chew the cud later at a safe place and eat it again).
Another indication of the non-essential nature of the canopy of elephant foot yam is indicated by its single stem canopy that does not form new leaves nor grows. The stem comes out of the conical sprout and opens out like an umbrella, but that is it. If the leaves are cut, or the stem is cut, new sprouts do not turn up. Does’nt it mean that the elephant foot yam is not critically dependent on its canopy?
I searched for any findings on this “grow underground without canopy or photosynthesis” but could not locate any. I seek opinion of experts on this.
k vinod kumar–
the earth be green