How Long to Freeze Seeds Before Planting

To safeguard the survival and future of certain plant kinds, seed banks and seed storage containers preserve uncommon, exotic, and heritage seeds in refrigeration units or cryogenic chambers.

You probably don’t have a cryogenic chamber in your garden shed as a home gardener, and you also probably don’t need to preserve thousands of seeds for decades.

However, as long as leftover seeds are stored correctly in the freezer, the kitchen refrigerator or freezer will suffice.

Some seeds can be killed by improper freezing, although other seeds may be less picky. Many wildflower, tree, and shrub seeds, in fact, require a cold period, known as stratification, before germinating.

Plants such as milkweed, Echinacea, ninebark, sycamore, and others will shed seed in fall and then lay dormant under snow over the winter in cold areas.

Rising temperatures and moisture in the spring will cause these seeds to sprout. Seeds like this, however, will not grow without the preceding cold, dormant period. This stratification phase is readily replicated in a freezer.

Using Seeds that are frozen

Seeds stored in the freezer will have more stable temperatures than those stored in the refrigerator.

A seed’s storage life might be cut in half for every 1% rise in humidity. Similarly is the case in every 10-degree A -12 C. (F.) temperature rise can also cut seed storage life in half.

Can Seeds be frozen before planting?

Freezing seeds does not hurt them and, if done correctly, can considerably increase their lives.

Every seed bank freezes its seeds for long-term preservation! When it comes to freezing, humidity is more of a problem since a burst of warm damp air on frozen seeds might destroy them.

How long to freeze seeds before planting?

To stratify seeds, freeze them for 48 hours before germination. This is not essential for all seeds, but we have employed this procedure with great success for over 30 years. When completed, seal and store any leftover seed in the freezer — it will keep longer.

Read also: How To Store Seeds For Decades

How long do seeds need to freeze to germinate?

Most seed that requires a winter frost will require two to three months to break dormancy.

In the freezer, how do you cold stratify seeds?

  1. In a mixing dish, combine 1/4 cup sand (or more).
  2. Fill the sand with the required amount of seed.
  3. Seal the sand/seed mixture in a ziploc bag.
  4. On the bag, clearly label the variety and the date.
    5..Refrigerate for one month before to planting.

Can seeds grow after been refrigerated?

Simply placing the seed packet in the fridge will not work: there is no moisture! The length of time the seed must be cold stratified will be specified on the seed packaging.

We cannot ‘pre-stratify’ these seeds since the embryo within the seed swells up and prepares to develop when placed in cold and damp circumstances.


When it comes time to plant, remove the seeds from the freezer and let them thaw at room temperature for at least 24 hours before planting.