Starting Perennial Seeds
Annual seeds germinate quite readily at room temperature, but some perennial seeds need some special treatment before they will germinate.
Some perennials will germinate at room temperature too, you can try it out… but the majority of perennials need cooler conditions to break the dormancy of the seed.
They benefit from being chilled, either before or after planting, to speed up germination - or even to result in germination at all. The proper term for this is stratification.
Methods of Stratification
Choose one of the following methods:
Keep the seed in the fridge for a couple weeks before planting
Keep the seed in the freezer for a couple weeks before planting
This should only be done if you’re sure that the seed is absolutely dry
Lay the seeds on a piece of paper towel; wet the paper towel, put it in a bag, and put it in the fridge for a couple weeks. Then, either:
bring it out to room temperature, still in the bag, and wait for the first signs of a tiny root and plant the seeds that have sprouted
bring it out to room temperature, and plant the seeds
Plant the seeds in moist soil, wrap the tray in a plastic bag, and set it outside in the shade for 1.5 - 2 weeks (when the temperature is fluctuating between 10C and slight freezing); then bring the tray inside, still covered, and watch for germination.
In general, Method #4 is best for a home garden scale. It is easy, efficient, and works well for most seeds.
Large seeds, especially if they have a hard coat, benefit from method #3, since the extra moisture helps soften the seed shell. In this case, you may not even have to put the moist paper towel in the fridge, as they may germinate just fine with the ample, consistent moisture.
The rule of thumb is: if you have perennial or herb seed planted at room temperature, and it doesn’t germinate within about 10 days, then chill it for 1 - 2 weeks, and watch it again for germination.