How I store my seeds

I love growing from seed in the spring, watching hundreds of small miracles occurring in a season inspired by hope.  Each seed is precious, and their viability depends on how well they are treated and so as the keeper of the seeds I have a responsibility.

There is nothing more annoying and frustrating than lovingly sowing seeds and doing all of the right things to ensure their care during the germination process, only to wait endlessly for seeds that are never going to pop up.  A lot of the effectiveness of seeds comes down to how they have been stored.

Ideally fresh is always best for seeds and some have fickle features where they need to be germinated in the light, prefer a certain temperature range to get going or scarified and scratched up so they are able to absorb the moisture needed to awaken the life within. For the most part edibles just need the standard care and should pop up with a 10 – 14 day window, provided everything is as it should be, with warmth and moisture in a seed raising mix that supports the emerging seedlings with the right structure and moisture retention capabilities.  It always pays to check the requirements of seeds that are new to you.

When buying seeds they, more often than not, come in sealed foil packets with an expiry date stamped on the back.  This is so the grower has an idea how fresh the seeds are and when grown within the date should – barring user error, have a successful germination experience.  Once past this date the germination rate doesn’t automatically disappear into oblivion, it just begins to reduce over time at around 10% per year.  So you can still used ‘expired’ seeds but as each year passes, you just need to be a little more generous when sowing seeds.

However once opened, then external factors are at play.  The environment that seeps into the opened packets needs to be supportive of the exposed seeds and do them no harm. 

For the best results seeds should be kept dry as exposure to moisture can begin the germination process, however only a little bit of moisture won’t be enough enable complete germination and the seed will abort the process, or invite mould or mildew, which will both render the seed non viable.  Having said that enough moisture for full germination isn’t ok as we don’t want our seeds germinating in the packets and too much moisture can cause the seeds to rot, which we don’t want either.  Consider adding rice or silica sachets in with your seeds.

Keeping stored seeds in the dark is also important.  Sunlight is harmful to seeds and as with all organic materials it can speed up the natural decay process.  Things left in the sun can age, fade, dry out and shrivel up.  Seeds kept in the dark are protected from the harmful effects of the light and stay viable for a lot longer.

The other important factor for well stored seeds it keeping them cool.  This can be a bit of a Goldilocks problem. Too hot can be detrimental in similar way to light.  But too cold is also a problem.  It needs to be just right.  When you think about seed – it needs three things to germinate – moisture, a degree of light and temperature.  For most edible crops 12 – 15°C for soil temperature is about the lowest and most like it a lot warmer around 18 – 20°C.  So ideally keeping them below a temperature that is telling them to germinate and well below a temperature that can harm them is best.  

But the key is cool, not cold.  They don’t need to be stored in the fridge, as this can have too much moisture floating about and can fluctuate with the opening and closing of the fridge door as we mindlessly check throughout the day for snacks that aren’t there and won’t magically appear with extra checking.  These conditions can reduce the viability for seed health.

Even worst would be the freezer.  Experts store seeds in special freezers that are beyond our domestic capabilities and have processes to ensure no harm comes in the defrosting process.  In a home freeze / thaw process, the moisture stored naturally within the seed can freeze and expand and upon thawing burst cell walls and destroy the seed.  So it isn’t recommended to freeze seeds at home, just keep it somewhere cool, like in a dark cupboard or unheated shed.

The final thing to protect the seeds from is rodents.  There is nothing more disheartening to reach into your seed collection in the spring to find you have been feeding rats and mice over the winter months.   The best kind of container is a rodent proof metal box.  An old bikkie tin from an op shop is perfect.  If it will keep the cookies fresh then it will be perfect for your seeds. 

This eliminates plastic as a seed container if rodents are likely to be a problem as it won’t stand in their way – no matter how thick.  If they can sense there are goodies in there, they will do their darndest to reach inside.   But plastic also comes with its own problems – especially plastic bags as the seeds are at risk of sweating, or trapped moisture from the environment can invite mould and mildew and ultimately rot.  A paper bag is preferable over plastic to control the atmosphere around the seeds.

Other than that, the viability of seeds is down to genetics.  Parsnip and onion only really last a year without dramatically reduced viability no matter how well you store them.  Other seeds can last a lot longer – some scientists recently germinated some date seeds that were stored away in what turned out to be ideal conditions from Herod’s Palace around the time of Jesus!

So the key is, look after your seeds and they will look after you for as long as they are able.

Come again soon – we are in the optimistic season.

Sarah the Gardener  : o)