SO... what care/conditions does it need as a houseplant? I'm not terribly familiar with begonias in general. It's in a western facing window with good general light. Do I fertilize through the winter (when, how, what?) ? It went gangbusters outdoors with no help at all but I can already tell from the leaves it's dropping inside that it isn't happy with the transition. (I admit that I didn't do a lot of in-and-out conditioning with it, just sprayed it with a natural insecticidal soap and brought it in...)

Any general advice on how to help it thrive would be appreciated.

The plant, in other years, has had difficulty which brings up certain requirements of any houseplant; namely....good drainage, water not being allowed to sit under it, decent enough sunlight, albeit not directly....fresh potting soil in a clean pot....definitely not garden soil, watered only as it can use it...yet stay moist.

What might cause a plant continued problems since it does require it be kept in a moist condition...the soil, having to be kept moist, has nothing in between it and drainage holes...possibly setting up ...NOT MOIST...but WET conditions because it has nothing to prevent it cuz the soil is next to the drainage holes. The drainage holes might well plug up and continued watering only causes WET ..instead of moist and even tho the surface might dry out somewhat...the roots are continually surrounded by too wet conditions...causing the problems you have experinced in other years.

If this might be the cause, then the cure is to make sure there is something in-between the soil and the drainage holes to prevent over-watering. Shards of clay work great, stones of size....pretty well anything that prevents the soil from plugging up the holes.

What does the fact that it did bloom in the house last winter/spring -- but not during the summer outdoors, when it fared much better in terms of foliage but never produced blooms -- mean, if anything?