Some seed needs a period of moist cold ‘to break dormancy’ and awaken them into germination and growth.

Many alpine plants, trees and shrubs require exposure to moisture and low temperatures for 30-90 days. This is the conditions they expect in their natural environment and gardeners need to replicate these conditions.

These requirements we call ‘Stratification’.

Methods of Stratification

• Seed can be sown in January or February and left outside in the UK. Then depending on the species they can be brought into a temperature of 65-70ºF to germinate.
• Mix the seed with some damp sand, vermiculite or small amount of damp peat. Place in a plastic bag and put the bag into a fridge for 6-8 weeks. Check for signs of germination (sprouting) by looking through the plastic bag.
• Seed which then fails to germinate should be left outside for another winter. Sometimes they need two cold spells before germinating. Never give up as  seeds want to grow and are programmed to help the species survive.
• Alternatively, the seed may be sown in small pots filled with moist soil and then the whole thing enclosed inside a plastic bag before placing inside a common refrigerator.
• Juniper, Cotoneaster and some other species need a period of warmth followed by a cold stratification. So they are best sown in warmth for upto 3 months then placed in a fridge for 3-8 weeks.
• After undergoing the recommended period of stratification, the seeds are ready to be removed and sown in the nursery bed for germination.

Stratification Tips

• Use of a fungicide to moisten your stratifying peat or vermiculite will help prevent fungal diseases.
• Outdoor stratification leaves seed open to the natural elements and animals as nature intended. For this reason the number of viable plants may be reduced.
• Avoid torrential rain or the seed or even compost  may be washed away.
• Different seeds should be placed in different labeled bags rather than putting them all into one bag.
• Most seedlings benefit from good air circulation which discourages fungus growth and promotes sturdy stems.
• Potting and germinating medium  is not critical as long as the soil is light, gently firmed down but not  compacted.