I have some small perennials in pots in a hobby greenhouse. How should I treat them so they will get cold and bloom next season?
It sounds like your perennials are protected in the greenhouse, at warmer temperatures? I would decrease the temperature maybe 5-10C (10-20F) a week until it is about 5C (40F) or a little lower. It doesnt sound like the plants are large enough, or established enough to take much freezing, hence keeping them about this. That should give them some cold, which hopefully will help blooms. Perennials all vary, some need cold, others dont, and some vary in the amount from 4 to 12 weeks. It is the longer days in spring that gets them growing again, so the sooner in fall you can give them cool temperatures the better, so sufficient time if they need cold, before spring. I would still keep them fairly cool even when they start growing, otherwise they might grow too fast, bloom, or get too leggy before you can put them out safely.
