How Long Do Cannabis Seeds Last? Storage Life and the Right Humidity

Stored in ideal conditions (cool, dark and dry, around 4-8 °C / 39-46 °F and low humidity), cannabis seeds can stay viable for more than 5 years; in so-so conditions, expect closer to three. Storing them right lets growers keep a valuable genetic stash on hand, plan future grows and plant when the timing is right.

So how long can you keep weed seeds before they lose their ability to germinate? It comes down to a few factors: storage conditions, how good the seeds were to begin with, and the specific strain.

Below we cover the key points of cannabis seed storage and how to keep your seeds' germination potential intact for as long as possible.

How to store feminized and autoflower seeds

Cannabis seeds are living things, so they need specific storage conditions to stay viable and able to germinate. Store them badly and over time they lose their germination power, which can slow germination down or stop it altogether.

Normally, cannabis seeds should sprout within 48 to 72 hours, but poor storage can stretch that to 5, 6 or even 7 days, or keep them from germinating at all.

Ideal storage conditions for cannabis seeds

To get the longest life out of your seeds, you need to keep them in the right environment. Most seed shops and distributors store them in refrigerators to recreate ideal conditions. Those conditions are:

• Temperature: between 4 and 8 °C (39-46 °F).
• Relative humidity: roughly 10% to 20%.
• Darkness: keep seeds away from light, since it can wear down their ability to germinate.

Best ways to store weed seeds

One of the best ways to store cannabis seeds is in an opaque, airtight plastic container. To control humidity, toss a few silica gel packets in with them so humidity stays in the ideal 10-20% range.

Keep the container in the fridge, ideally in the crisper drawer, since it runs slightly warmer than the rest of the fridge, right in the 4 to 8 °C (39-46 °F).

How long do cannabis seeds last?

In ideal conditions, a cannabis seed can stay viable for more than 5 years. If storage conditions aren't great, though, that window can shrink to about three years.

So if you're planning to plant your seeds soon, say in a few days or weeks, you don't really need to put them in the fridge. Just keep them somewhere cool and dark, in their original packaging, and they'll stay viable.

How humidity affects cannabis seeds

Humidity is one of the most critical factors for keeping cannabis seeds viable. Different relative humidity levels can have big effects on seeds, from triggering germination to causing them to deteriorate or get damaged. Here's how each humidity range affects cannabis seeds:

Relative humidity levels and what they do

80-100% relative humidity

Effect: seeds germinate.
At these high humidity levels, conditions are perfect for germination. That's exactly what you don't want if you're storing seeds long term, since premature germination can ruin them.

40-60% relative humidity

Effect: more respiration and a risk of fungus.
In this range, seeds ramp up their respiration, which can cause problems like fungal growth. Avoid these levels to keep mold and other issues from compromising your seeds.

20-30% relative humidity

Effect: short-term storage.
This range works for storing cannabis seeds short term. They can stay viable for a few months without significant deterioration.

18-20% relative humidity

Effect: medium-term storage.
These humidity levels are suitable for medium-term storage. Seeds can stay viable for several months up to a year.

12-14% relative humidity

Effect: long-term storage.
This is the sweet spot for storing cannabis seeds long term. Keeping them in these conditions can preserve their viability for several years while minimizing the risk of deterioration.

8-9% relative humidity

Effect: shorter lifespan than at slightly higher humidity.
You can store seeds at these low humidity levels, but they may not last as long as seeds stored at slightly higher humidity. Balance is key, because humidity that's too low can also hurt their long-term viability.

Storing cannabis seeds: the takeaway

Controlling humidity is essential to storing cannabis seeds properly. Keep them at the right humidity and they'll stay viable and ready to germinate down the road.