Your climate is going to be the primary problem. Ranunculus tubers cannot freeze but should be shallowly planted. The ideal location for growing them has cool winters that never drop below freezing. It's best to plant the tubers in the fall so they can send out roots and leaves throughout the mild cool winter. Then in the spring they will bloom and then go dormant as the weather heats up. You can try planting them in the spring (as I've attempted) but typically they only get marginally established before the warming weather triggers blooming and then they bloom poorly and briefly because they are not fully established. If you have a greenhouse or hoop house that you can keep a bit above freezing all winter that should work, but don't let it overheat.

Steve
THANKS! I have an unheated greenhouse, that I THINK I can keep above freezing. I did last year, though last winter was wierd. So I am going to try. Thanks also for you advice re planting in spring. New England spring can be tempestuous. . So I am going to hold some back, and plant in soil as early as greenhouse will allow, for comparison. Now I know what to look for!

Are they sensitive about winter moisture?

Well, if you are able to keep the temperatures above freezing and they have leafed out and are trying to grow then they will need some moisture. By contrast, during the summer when they are dormant they should be dry.