SummerPerson~
By "re-bloom" I'm taking it that you mean blooming a year after the initial bloom rather than a second or third flush later in the same season.
Before I get into bulb resting, I'd like to say that if a bulb hasn't had all that it needs culturally to fully develop those inside, it likely won't bloom the next year. Or it may produce fewer stems. Continued culture that is inadequate may result in smaller flowers and/or fewer flowers on the stem, even after your bulb regains strength.
It is most important for a "new bulb" (newly purchased and planted) to be well-grown in the first year after potting. It has to produce a bloom stem, a full set of roots, and perhaps some of the new foliage using the nutrients stored in the bulb. It also has to continue developing the buds of future scapes. In doing all that, the bulb loses size and has to replace all that to return to "blooming size" or better and top health during that first season, or it may not bloom at all. A large bulb may have embryonic buds still forming, but these may abort if the bulb declines too much. All that bulking back up may not happen right away. In my experience, my bulbs seemed to "pack it on" from late summer to fall.
If I remember correctly, in a optimally-grown bulb, it takes about a year from bud initiation to the emergence of the scape.
So, a plant needs to be well-fed and watered and have adequate light in the growing season to make those buds grow and bring them to fruition. This may be the most critical aspect affecting future blooming. Six hours (total) of direct sunlight isn't too much for most Hippis in my experience.
Veronica Read recommends a "cool rest" rather than a complete (leafless) dormancy (allowing the soil to go bone dry and the plant losing all foliage) for the modern hybrids. This rest would be at a reduced temperature, with good light, and moisture applied but at a reduced rate.This method aids in allowing the bud inside to mature and gets everything set for blooming, since the roots will still be replacing lost moisture and some photosynthesis will still be going on, though on a low level.
(Read's book is a wonderful resource and you might get a copy from your local library if the price is prohibitive. It isn't cheap. ;-) )
Bulbs will naturally rest when they need to, and her method is one that keeps the bulb green (that is, with green foliage) and the root system intact. Keeping your plants potted was a good move. If you had taken them out of the soil, the roots would have dried out making it necessary for the bulb to grow a new set later on, using bulb resources. Also, if the plant is green with intact roots, it will be taking in moisture as it blooms to replace what is lost in the process. This results in less shrinkage of the bulb.
Some bulbs will lose all foliage anyway, due to their nature or cultural conditions. If they do, it's OK. You might choose not to let them do bone dry for a long time and give them a light moistening-- but not too much-- from time to time. Just enough to keep the roots from drying out too much. I have let them go bone dry for weeks or a couple months and they've been OK. So, if they go leafless, just let them rest at 55-68.
There is a range of temperatures for the "cool rest". Read suggests about 68F in most cases. Between 55 and 65 F day and night is fine. The day temp can go a little higher, but I would say no more then about 68F in the day. Of course, this is a guideline and there is a range that works, so don't fret too much. I have had bulbs get very cool night temps outside (below 50F) with days in the 70's and that gave enough rest for certain ones. It's the soil temperature that is the key, not so much the air temps.
One thing though is curious: Bulbs can have a re-blooming (or two) later in the same season without having a weeks-long cool rest.
I don't know personally that the dwarf types are harder to get to re-bloom. I think that it may be a matter of having fewer buds in development making it even more critical that they have a good growing season.
Good growing!
R.
