Sow the seed right away, Giles - it should germinate in spring. Pot could sit outside until you see germination. A potting compost of grit and humus is best.
This charming plant was the subject of plant portrait in the International Rock Gardener (IRG) issue 17 of May 2011 by Kirsten Andersen and Lars Hansen :
http://www.srgc.org.uk/logs/logdir/2011May261306444476IRGMay2011.pdfwhere they included this advice ....
"Dicentra peregrina is in our opinion the most exciting among the genus Dicentra. We have grown it
for about 20 years in our garden in Denmark. In some years all our plants almost disappeared but they
have always managed to seed around and the seedlings will grow to flowering sized plants in one to
two years. We have tried to use different locations and types of soil through the years and we have
had the best result when we put the plant on a southern slope with roots and rhizome positioned
behind a stone. The soil must be well drained and contain humus to ensure adequate moisture in the
root zone. It is important that the soil never dries out completely.
Dicentra peregrina is easy to propagate from seed. The seeds should be sown immediately after they
are harvested in July/August. The seeds germinate in the following year in February/March and usually we have a very high germination percentage. It is also possible to divide the plants in late autumn or early spring while they are dormant. We don’t use this method since the propagation by seed works perfectly.
With regard to the cultivation of
Dicentra peregrina it is undoubtedly an advantage that we have
relatively cool summers in Denmark. The average temperature in June, July and August is around 15.3 °C. "
