Hi! I found this on one of the websites I was looking at:

Propagation
Seed - best sown as soon as it is ripe in a greenhouse or cold frame[200]. Germination is usually very quick and good[78]. Prick out indoor-sown seedlings into individual pots when they are large enough to handle and plant them out in the summer. Another option is to pre-soak the stored seed for 12 hours in warm water and sow in an outdoor seed bed in early spring. These plants an be allowed to grow on in the seedbed for two years before planting them out in the winter. Cuttings of mature wood in late winter planted in the open ground[200].

I found at http://www.pfaf.org/database/plants.php?Laburnum+anagyroides. Good luck!

thank you! I must be cleverer with my googling next time...