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.
