How to grow cranberries from the supermarket. Based on my gardening book Grow Your Groceries! Cranberry seeds require stratifying for them to germinate. Stratifying means chilling them in a fridge with a bit of moist compost for a few weeks prior to sowing. After stratifying, sow seeds into peat free, ericaceous compost. Ericaceous compost is a type of acidic compost. Cranberries require acidic conditions to grow. Cranberries also require moist conditions so water regularly. Use rain water not t