To clarify, Astrantia seed germinates in the cold (around 40F), not warm. If you see them sprout at 55-70F, it's because the seed germinated in the 40F range, and emerged at warmer temps. Jonna is right that they still need the initial warm period, but you must be sure there is ample time in the 40F range (not below freezing) to allow for the process before temps go above, say, 55F.
