Cold stratification of seeds

Many seeds are otherwise easy to grow, but must be cold stratified (usually for between one and four weeks) or they absolutely won't sprout. This means providing a period of cold to mimic winter conditions and seeds must be moist for this to be effective. There are different ways of doing this.

If you obtain seeds while it is still winter (before the beginning of March) an easy way of growing them is to sow in a seed tray or other container which you can then leave outdoors. Cover the tray with a sheet of glass, propped up at one end to allow air to circulate and water to run off. Cold-stratification will happen naturally and the seeds will begin to sprout when the weather warms up (or they can be brought into a warmer environment after a suitable period in order to force germination).

At other times of the year, seeds can be sown in trays of damp compost and put in a plastic bag in the fridge for a week or more. If space is tight, scatter seeds on some damp tissue, fold it up, put it in a plastic bag and put that in the fridge. Sow the seeds in compost at room temperature after the stratification period. Seeds will start to germinate within a week of changing temperature and seedlings can be planted into individual pots when they are large enough to handle.

The following plants have seeds that need cold-stratification. The pages have more planting details and specific information on the length of the cold period required for each.

Sweet violet (Viola odorata)
Scots lovage (Ligusticum scoticum)
Caucasian spinach (Hablitzia tamnoides)
Virginia skullcap (Scutelaria lateriflora)
Alpine/woodland strawberry (Fragaria vesca)