Here's what Tom Clothier's site has to say about starting it indoors.

Alchemilla alpina, epipsila, erythropoda, hoppeana, mollis, saxatilis, and xanthochlora , Sow at 18-22C (64-71F) for 2-4 wks, move to -6 to -7C (19-21F) for 4-6 wks, move to 5-12C (41-53F) for germination

Self sown lady's mantle seedlings appear readily in spring in my yard - it is a very good candidate for fall sowing.

There is nothing like Lady's Mantle in a bouquet, the smell is wonderful and that frothy yellow really makes the other flowers stand out.

Here is a link that might be useful: Tom Clothier's seed starting site