To all (especially Rob),
Here is yet another chapter of my never-ending crusade to disassociate U.reniformis from the epiphytic Utrics...
Unfortunately in the past, popular CP books lumped U.reniformis together with epiphytic Utrics simply because of its size. It's true that there are 2 epiphytic species in its section (Section Iperua): U.nelumbifolia (exclusively epiphytic) and U.humboldtii (optional epiphytic). The 2 other species in its group (U.nephrophylla and U.geminiloba) are only known to grow as terrestrials.
As for U.reniformis, I do not tire to say that 99.999% of the times it is TERRESTRIAL!!! The only case I know of where it was growing anything close to epiphytic was when a friend found some growing among dead leaves surrounding the base of a large terrestrial bromeliad.
And for anybody wanting tips on cultivating this species, I'll repeat what I've said before: it's a very widespread species and it grows from sea level to nearly 3000m altitude, in boggy soil or nearly dry sand, from pure moss over rocks to coastal habitats which may be slightly salty, in alcaline to acidic conditions -- you name it, and it's there!
So it would probably be best to ask WHERE they come from when somebody offers you plants. At least one thing they ALL have in common is a winter dry season. Since most are seen in flower in the winter, one can guess that either dry stress or photoperiod are responsible for flowering, but my field observations suggest its dry stress.