Stratification is a treatment of seeds used to jump-start them to germination.
Many plants need a period of winter chilling to break the seed’s dormancy for spring germination.
Stratification achieves this artificially – most commonly by simply exposing seeds to cold.
Cold Moist Stratification
- benefits many species, including fuchsia, sedum buddleja and lavandula
- place seed in a clear plastic bag filled with moist (but not wet) coir, somposted bark, or equal parts of these with coarse sand, perlite or vermiculite.
- seal the bag and chill in a refrigerator below 5 degrees C for 4-20 weeks. The time depends on the type of seed so seek guidance on the particulars.
- shake the bag periodically. If you see signs of germination within the bag, then sow immediately.
Warm Moist Stratification
- benefits actaea and some lilies
- place seed in a bag as above.
- keep in a warm place (such as an airing cupboard) at 18-24 degrees C for up to 12 weeks.
- move the envelope to the fridge and provide a spell of cold stratification as above.
- plant out when you see signs of germination.