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storing hemp seeds

Seed Storage

For information on how to store seeds please continue reading down this page. To read more about why we believe seeds need to be stored and preserved please see the About Us page.

Basic Points in Seed Storage

  • Seeds require a cool and dry location in which to be best stored. Temperature and humidity fluctuations are seeds’ worst enemies.
  • The most vigorous seeds at harvest time will keep the longest in storage. (As a principal we only sell the brands that have the most vigorous seeds.)
  • Improperly dried seeds can deteriorate drastically over time. (The seeds we sell have been dried properly before they are packaged and you only need to store them in a cool, low moisture environment for optimum preservation).
  • Bags and jars should be clearly labelled at time of storage with strain name, date and other relevant information about the strain you are preserving.

Moisture

Seeds carry on life processes, at a low rate, whilst dormant. Moisture they absorb from the air combines with stored nourishment within the seed to form a soluble food, which then combines with oxygen from the air to release water and heat. Too much moisture in the air will cause the seed to burn up its stored food too quickly producing excess heat which will further lower the seeds ability to germinate. The need is to keep these exchanges to a minimum during storage to prolong life in the seed.

6-9% moisture is ideal for long term storage of hemp seeds. A test for moisture levels shows that hard shelled seeds like hemp seeds shatter instead of mashing at around 8% moisture when placed on concrete and struck with a hammer.

Silica gel, often used in the drying of seeds, can also be used to help maintain stable moisture levels within a permanent storage container. Equal weights of silica gel to seed are used. In general hemp seeds weigh between 0.01 and 0.02 grams and our silica gel sachets contain 0.5g. We recommend seeds are kept in aluminium zip-lock bags and stored inside seed jars along with the correct amount of silica gel to maintain low moisture levels. Be aware that you can seriously damage seeds by reducing moisture levels too much, so do not use too much dessicant. Silica gel, aluminium zip-lock bags and seed jars are all available to buy from our Seed Storage section.

Temperature

Seeds can survive temperatures that would kill the parent plant as long as they are thoroughly dried. Excess moisture in seeds that are then frozen can potentially freeze, damaging the seed.

Seeds need to be stored in a cool or cold place. Therefore, locations at floor level are preferable to those nearer the ceiling which can be significantly warmer. However, for long term storage, placing seeds in the fridge or freezer is ones best bet, as long as moisture content of the seed and storage container is low and the container is air-tight. The ideal temperature in a refrigerator is around 4 o C.

A freezer is best for long-term storage of seeds although you need to make sure:

  1. You do not take the seeds out too much or for long enough for the temperature change to affect the seeds.
  2. When you want to remove seeds from the freezer, you leave the container closed whilst the seeds warm to room temperature or otherwise condensation will form on the seeds.

Light

Similar to moisture and temperature, light can help stimulate and support the germination process. And, just as many foods, pharmaceuticals and chemicals rapidly deteriorate when exposed to light, so also is seed viability and vigour affected by being exposed to light during storage.

Seed Storage Problems

Mildew/Mould

Seeds which have not been dried to the correct moisture content before being sealed in containers, can and frequently do rot. A simple test: after “drying” and placing in closed glass jars, the appearance of condensation on the inside of the jar within a few hours indicates the need for further drying. Silica gel should help with this.

Insects

Insects that may have escaped notice can wreak havoc on stored seeds. A few pinches of diatomaceous earth (DE) is a safe, inexpensive and non-toxic way of protecting seeds against insect damage. It doesn’t take much; just be sure to lightly coat all seeds before final sealing and storage. DE is available at most garden centres.

Rodents

Seeds which are not stored in glass or metal can provide a veritable banquet for mice and other small vermin. Make sure all seeds are kept in well labeled metal or glass containers.

Learn about how to properly store seeds. This page covers the basics points on how to store your seeds to ensure you get the best results. Find out more now.

How to Store Cannabis Seeds

A reader recently asked us a couple of questions about storing cannabis seeds. We realized it was info we haven’t covered on the site yet, so we figured it was worth a post. Here’s what he wanted to know:

  • How long can you store cannabis seeds for? Is there a maximum amount of time they’ll remain viable?
  • What is the best method of storing seeds?

How long can you store cannabis seeds?

The consensus is that cannabis seeds should last up to a couple of years stored in a cool, dark place—or even up to 5 years if stored really well.

In fact, even with beans much older than that, if they’ve been well stored, apparently it can be worth giving sprouting them a try—cannabis is pretty hardy. But we wouldn’t aim for that!

Generally, the fresher the seeds the better, in terms of maximum chance of germination. Up to a few months is probably ideal.

(But when collecting seeds from your plants, don’t harvest them too early. They’re best harvested at the end of a grow, when they’re a darker color, mature.)

So, on the one hand, there’s no real ‘use by’ limit for cannabis seeds.

But generally, the longer they’re stored, the lower the germination rate. However, up to a couple of years, the risk of non-germination is still pretty low.

For our complete guide to buying seeds online, click here.

Learn how to select a reliable seed company and discover some great strains for beginners.

What is the best method for storing cannabis seeds?

The best way to store cannabis seeds is probably in black film canisters kept near the back of the fridge. With either a little food-grade silica crystal package or a little uncooked rice at the bottom of the canister, to absorb any moisture and keep them dry. For extra airtightness, put the seeds and silica/rice in an airtight baggie first, and then inside the canister.

Of course, now we’re all using our phone for photos, far fewer of us have film canisters just lying around…

If you’ve bought your seeds, it’s likely they came already vacuum-packed, airtight, with a dessicant package. So if you haven’t disturbed the packaging, then use that and store it inside something lightproof.

That should be more than good enough for a few months of storage.

Storing cannabis seeds longer term

For longer term storage, vacuum-sealable, or heat-sealable containers are what you need. A glass mason jar would work, for instance, so long as you put the jar or the seeds inside something light-proof.

Whatever container you use, though, the aim here is simply to keep out heat, light, oxygen and excess moisture—to slow down the life cycle of the seed to an absolute minimum, stop it ageing, stop it from beginning to germinate. Too much of any of those factors and the seed will attempt to germinate.

Keeping the seeds nice and cool also helps stop them from drying out completely and prevents any bacteria from activating.

Finally, keeping temperature and humidity as stable as you can helps extend lifespan too. (See below for optimal temp and humidity ranges.)

All in all, the more you can do towards all of those aims, the better.

Which is why storing your container towards the back of the fridge is best, where it’s least moist and temperature is most stable. And, in most fridges, the veg shelf is usually where the temp is closest to ideal.

Store cannabis seeds in an airtight container

Yep, opening and closing the fridge door can create condensation, as well as temperature changes within the fridge. However, if the container/package is well sealed, condensation shouldn’t be a problem. And as we said, towards the back of the fridge, changes in temp should be very minimal.

Nonetheless, the frequent opening and closing of the fridge door is one reason why some growers recommend storing your airtight light-proof container in the freezer instead. However, not everyone agrees…

Can you store cannabis seeds in the freezer?

Lots of people advise that when storing seeds for longer than a couple of years, put your container in the freezer instead of the fridge. However, many others argue pretty convincingly that unless you have the kind of freezing equipment that most home growers don’t, then freezing damages cells—which kind of makes sense.

Honestly, though, we just don’t know! If you check their FAQs, even seed banks seem to be a bit divided on this … But anyway, if you go with freezing:

The advice is to make sure not to defrost the seeds until you need to use them—the more often they’re defrosted or partially unfrozen the less likely they are to germinate. And leave them in the container at room temperature to slowly defrost when you do want to use them.

Those who do argue for freezing say freezing just the once shouldn’t do too much damage.

Ideal temperature and humidity levels for storing cannabis seeds

Here are the recommendations from Ryan Riley’s Growing Elite Marijuana for seed storage:

Temperature and humidity are the most important factors affecting seed quality during storage (humidity being the more important of these). Marijuana seeds absorb moisture from wet atmospheres and dry out when placed in dry atmospheres. Seed storage life is doubled for every 1% decrease in moisture content. The problems of maintaining seed germination [i.e. viability] increase with seed moisture content.

Seed moisture above:

  • 80-100% — Seeds drown and become wilted after any more than 12 hours
  • 40-60% — Germination occurs
  • 18-20% — Heating may occur
  • 12-14% — Fungi grown on and in the seed
  • 8-9% — Insects present become active and reproduce

Heating is caused by the natural respiration of cannabis seeds, of fungi and bacteria in and on the seed which may build up rapidly in a moist environment. High moisture levels and high temperatures will kill cannabis seeds as quickly as an invasion of micro-organisms and insects, so be careful.

Stored seed life is doubled for every 41ºF (5ºC) reduction in storage environment temperature.

Refrigeration to at least 41ºF (5ºC) is recommended (yes, this is slightly warmer than regular fridges). The cooler the temperature the more slowly seed vitality declines. This rule apparently continues to apply even at temperatures below freezing. At 41ºF (5ºC) and below, insects become inactive.

When the above storing conditions are met, storing cannabis for five years with high germination success rate is entirely doable.

(Want to know more about Ryan Riley’s book? We’ve got a review here.)

Similarly, Jorge Cervantes’s Grow Bible recommends keeping humidity below 5% and keeping temp at 35-40ºF (2-5ºC).

Ryan Riley also advises (as does Jorge Cervantes):

Make sure to label the container/package with strain, quantity and date received to make storing easier.

It can be very easy to forget details like that later—or even what was in the container in the first place!

That pretty much covers it.

Got any more questions for us? Email us at [email protected]

We’re always happy to hear from readers—and your questions really help us to write more of what you want to read about.

What's the best method of storing cannabis seeds? How long can you store them? Fridge or freezer? MaryJane has everything you need to know.