October 2016 issue of the Cornell Flower Bulb Research Program Research Newsletter:
Another way to reduce root growth is to simply give them less time to grow. We learned this from hydroponic tulips, where bulbs are first cooled dry, and planted after a relatively long period of dry cold (12-14 weeks perhaps). One of the real challenges in developing hydroponic forcing was to reduce root mass in the trays. It took a number of years to fully realize that cut tulips need a relatively small root system when they are grown hydroponically, and the same is probably true for pot tulips, although the root mass needed in a pot is likely to be somewhat larger than in
the hydroponic situation. The caveat being, uniformity of all 6 bulbs in a pot is important.
Read the whole article. Starts on page 5.