Posted: 20/03/2017 at 16:05
I've only done this once, years ago, when I nicked a few hips off some rosa rugosa shrubs in a public car park one autumn. I sowed them sparsely in a small window box, covered the seeds with about 1/8" of compost and then left them outside for the winter. The next spring they germinated and grew into enough small plants to grow on and make a hedge.
This chilling process is known as stratification. You can cheat by mixing your seeds with some slightly damp compost and sealing them in a bag and keeping them in the fridge for a few weeks. Then take out and sow in trays as you would any other seed.