I've got the following from a Peruvian website. Maca grows at an altitude of 3800-4800m where it's boiling hot during the day and temperatures at night drop below freezing. It's a brassica and looks like a turnip, the foliage is sort of carrotty/turnipy and the root itself is between 3 and 6cm in diameter, 4-7cm in length. It's sown between September and December and harvested six to eight months later. It's left to dry out in the sun for up to 2 months (we're lucky if we get 2 weeks here!) and during this time it loses 75% of its original weight and the flavour changes from bitter/spicy to sweet. Once it has dried it can be ground up and has a shelf life of up to 4 years. It's even sold in supermarkets in Lima and they've started making liquers and sweets from it. It was an interesting site - said the native Andes people have been growing it since about 1600BC and when the animals taken over by the Spanish conquistadors didn't reproduce at those altitudes, the natives fed them maca and hey presto. It didn't say anything about soil type etc only that they don't use herbicides as nothing else will grow at that altitude! Perhaps it'll only work if you're up a mountain