For transplanting, it will depend on the size of the seedling. Martagons, probably not. I don't think about transplanting my marts into the garden until the fall season after they have produced a whorl of leaves (2-5 leaflets). This is usually in their second or third year of above ground growth.
At any rate, whether you transplant into the garden or keep them in pots, they will always prefer to be outside, where they can enjoy fluctuation day/night temperatures and far better light (even if they are in the shade). They will still need to acclimate from inside to outside conditions, and the earlier (with little or no foliage) is always easier. If they are just peaking out of the soil or not at all yet, minimum 32°F is OK, but if it goes below I would bring them in the garage. Your martagon seedlings will still be fine at 30°F.
