I have tried ampullaria on clay and peat soil on open ground and curious to find out if rafflesiana and bicalcarata will do well. The following were the results since november, 2007
i scoop up the peat soil to show. During rainy season the ground was sticky.
another raff form
bicalcarata was also doing well.
The reason they grow in the peaty conds - the ground are all opend up by tree roots( note fibrous roots intertwined with soil) hence soil are well drain. Now a trial if northiana will grow, O planted yesterday ;D