Plant Doctor Archive

How to stratify seeds

I HAVE a packet of aquilegia seed. The instructions on the packet say the seeds need "stratification" to germinate. What does this mean?

SEEDS of some plants won't germinate unless they've gone through a period of cold weather. It's a form of dormancy which prevents the seeds from germinating in autumn, putting their tender seedlings at risk of being killed off by cold winter conditions.

Stratification is the term used to describe how to trick the seeds into germinating when you want them to. Mix the seeds with damp sand in a sealed plastic container and leave for around 24 hours at room temperature to allow them to soak up moisture. Then put the container in the fridge and leave for 4-6 weeks. Check them every week or so and shake the container to aerate the mixture. Sometimes they'll actually start to germinate in the fridge - if this happens sow them straight away, sand and all, and put in a sheltered spot to germinate. Otherwise sow them after a month or so.

I've found that aquilegias often germinate quite well in spring without stratification. You could try direct sowing some and stratify the rest to see if it makes any difference. Good luck - let me know the results.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.