Does anyone know if older leek seeds have poor germination? I planted some that are 2 years old, and the germination has only been about 10%. Not sure if it doesn't like my new potting mix, or what the issue is.

Searching around, I see "2 years", "2-3 years", and "2-4 years".

There was some anecdotal reports of three years, and one guy claimed five years.

Of course it matters how you store them.
Ideally, stored seeds should contain 3-5 percent moisture in a Relative Humidity around 20%.
The length of time that seeds stay viable approximately doubles for every 10% reduction in their relative humidity. Thus seeds at 20% RH might last as much as 8 times longer than seeds at 50% RH. No wonder there is little agreement on how long they last!

Tellingly, on several sites where I looked, leeks had almost the SHORTEST viability reported of any seeds I noticed, except for onions, (and maybe lettuce and parsley) which that site reported as "1 year"

Hmm, High Mowing seeds gives "5 years" for lettuce and "1 year" for leeks.
http://www.highmowingseeds.com...

Maybe the answer is "don't trust the Internet unless you know the site.

This forum has a sticky thread that suggests this link:
http://www.hillgardens.com/see...
Leeks 2-4 years
Lettuce 3-4
Tomato 4-7


Those numbers sound plausible-ish to me.

If they're like onions, they don't keep too well at room temperature. I put my last pack of onion seeds in the refrigerator and I got 100% germination this year. Can't remember now if these are 2 or 3 years old, tho. But I know the previous pack didn't germinate well after being stored only for a year at room temp.