Does your greenhouse stay above freezing all winter? If the plants won't freeze out there, you can cut back on the watering, they will probably lose their leaves on their own, and put up new leaves and bloom in May or possible early June. If they would freeze out there, you would have to bring them in the house like any tender houseplant. Your "shop" would probably be fine. This late, it probably isn't worth forcing dormancy for bloom in mid winter. The most you are going to do is push up the flowering a month or two over letting them go dormant naturally. If you want to force dormancy, the pot needs to dry out completely and then be put into a cool dry place (above freezing) for at least 8 weeks. You can pull the bulbs or leave them in the pots. Just one warning: Last fall 's bulbs were specially forced for last Xmas' bloom. They may not bloom again this coming spring. It can take a year or two for the bulb to rebuild itself to produce new flower stalks. So even if you do bring them inside, they may just produce leaves in the spring. They aren't sick, just recovering from the commercial forcing. Good luck!
