Cold Stratification

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Cold stratification is the process of breaking seed dormancy by exposure to harsh winter conditions. This happens naturally outdoors but you might find yourself in a situation where you need to do this manually indoors.

Not all seeds require stratification. In fact, most vegetables don’t. If you stick to growing food like we do, you won’t be stratifying seeds very often. However, a number of herbs will benefit from stratification, as well as most perennial flowers and tree seeds.

A layer of newspaper under your workstation makes cleanup a breeze.

The process is simple. To stratify seeds, fill a module tray with seed starting mix and moisten until water runs through. Give it a few taps to compact the growing medium just a bit.

Sow 3-5 seeds into each module and press lightly to make sure they have good seed-to-soil contact.

Cover them in a few millimetres of moistened seed starting mix if you wish.

Wrap the module tray in cellophane so it’s air-tight and place it in the freezer.

If it is not air-tight, the freezer will dry out the tray and ruin the seeds.

Leave the tray in the freezer for the next month, removing it two or three times for 24-48 hours to simulate winter’s natural cycles of freeze and thaw.

That’s it!

But why do this at all? Well, some plants have a longer growth cycle than your local growing season allows. Starting them indoors early buys you weeks or even months of extra growing time before the weather is suitable for planting out in the spring.

If the seeds you’re starting indoors early will benefit from cold stratification, you’ll likely see better germination results if you stratify them.

Congratulations, you’ve cold stratified your seeds! Now keep them warm and moist and follow the growing instructions on the seed packet. Good luck!

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