Posted: 04/02/2014 at 11:10
Outdoors, they need a chill. Best sown in autumn. But worth getting as cold as you can now.
This applies to a lot of hardy perennials. It's what happens naturally. Seed is set, shed, and either germinates immediately of in spring. Hardy perennials never need heat to germinate, it's not what they expect.
Some seeds will germinate whatever you do with them but some, apiaceae (eg astrantias) and ranunculaceae (eg hellebores) in particular, are fussy about it