Hello,
I have U. sp. Kerala (which I'm pretty sure is the same plant) and it produces leaf-bladders very often. In my growing conditions, leaf-bladders occur when moisture and humidity levels are very high, and are present on quite a few species.
So far I've seen direct leaf+bladders on U. sandersonii (after flooding), U. flaccida, U. reniformis (once only), and U. mannii. U. longifolia, U. praetermissa (once or twice, on very young plants), and U. trichophylla (after flooding) sometimes do the leaf+stolon bladders, but I haven't seen bladders directly on leaves.. Low light also seems t