New to greenhouses. I'm planning on getting a 15x9 or 9x9 portable greenhouse to get a jump start on my seeds. I'm trying to figure out how to heat it for the early spring/late winter or if I even need to heat it.

I'd like to use it over my garden bed and I'm trying to figure out if I should grow seeds in the ground or in containers in the greenhouse. I'm leaning towards containers

The one I am considering getting states that at night it will drop to nighttime temperatures unless it's heated. Late winter obviously that's not too desirable for seeding

Any suggestions?

Thank you!