If you're a seed hoarder like myself, there is nothing worse than trying to propagate seeds and they are no longer viable even if the date says they should be good. Seeds do have a shelf life, but environmental influences (aka the way you store them) have a massive affect their viability.
I once accidentally left my entire collection of carrot seeds outside by accident. It was a hot day, it was a full sun position and basically the seeds cooked and were no longer viable. There was at least a dozen varieties of carrots that I lost. Devastating.
The right conditions to store seeds
Seed storage is the opposite to what you need for germination. You want a dry, cool and dark environment. By storing your seeds correctly you can double, or even triple their lifespan.
Storage containers for longevity
Our preferred method of storage container is glass amber (or darkened) jars with air tight lids. Zip lock bags are not air tight, and also are see through so it's likely they'll get a bit of light and humidity which can decrease their lifespan. You can pop your ziplock bags into an envelope the into an air tight containers though to combat this.
We did invest in some wallet type seed storage containers (found in the craft supplies shops). Whilst they look pretty, store seeds perfectly for easy categorisation, they are not air tight, so if you're wanting to get more life out of your seeds give them a miss.
Temperature for seed storage
Most vegetable seeds should be stored at around 5 degrees celsius for long term storage. If you do opt for fridge storage, make sure it's in an air tight container and it's recommended to use some method to take moisture out of the seeds by either silica gel or even dried milk powder and replace it often. I've found investing in some colour indicating silica gel the best as it will give you a really good indication if your containers are not air tight (or if the seed isn't dried correctly), you can reactivate the silica gel by popping in the oven or dehydrator and use it over and over.
If fridge space is at a premium and you'd rather the space for food your seeds will last outside the fridge. Until we started selling our seeds, a dark, cool, dry place was adequate for season to season planting. Just make sure your containers are air and light tight and placed in the coolest part of your house.
How to categorise seeds
There is nothing worse than trying to dig through lots of seed packets to find the one thing you want to plant. Or stumbling across something you wish you planted but missed your window!
Lots of people have many different systems and it is really a personal preference based on how you plant. For my personal stash because we follow moon phase planting I have 4 boxes that follow the roots, fruits and leafy greens and then an extra box for flowers.
You could also go via season (which is tricky when you’ve got cross overs of autumn and spring plantings), group them by types or just go alphabetically.
Find a system that works for you.
How long do seeds last
Every plant is different and it will all depend on how well they were saved to start with and how they are stored. Below I've listed some of the favourites that we grow and how long they last.
- Tomatoes – 4 years
- Beans/Peas – 3 years
- Lettuce – 6 years
- Broccoli/Cabbage/Cauliflower – 3 years
- Cucumbers – 5 years
- Zucchini – 4 years
- Beetroot – 4 years
- Swiss Chard – 4 years
- Carrots – 3 years
- Corn – 2 years
- Eggplant – 4 years
- Kale – 4 years
- Onion – 1-2 years
- Parsnip – 1 year
- Capsicum – 2 years
- Spinach – 3 years
- Pumpkin – 4 years
- Turnip – 4 years
- Watermelon – 4 years
If you want to learn more about seed raising, storage and more I have an online course inside my Dirt Lovers membership along with loads more courses, tutorials and resources for backyard food growing.
I'd love to know what's the oldest seed you've ever grown? Have you made a terrible mistake like I did cooking all your seeds in the sun? Leave a comment below!