How long are seeds good? Can I use those left over from last year?
If seed packages are sealed back up and stored in dry and cool [60-75 degree storage, most seeds will keep well for 2 to 5 years.
Here is a link that might be useful: seed vitality
Thank you Wayne you have made my day!!!
Or longer. many gardeners regularly use seeds that are 5-10 years old. If they were properly stored they will last for decades. There are a few exceptions like onion seeds.
Check out the FAQ on seed saving and seed storage over on the Seed Saving forum here.
Spinach seeds, too, don't keep well.
According to one of the scientists... they managed to grow a plant from 2,000 years old seed. As long as it's stored properly, they can last a long while.
I managed to germinate the pea seeds that were older than me (at that time, I was 20.) But then I'm having a trouble with germinating the spinach seeds after a couple years now.
To determine the viability of your seeds, you can take 6 seeds and placed them in a moisten paper towel. Put the towel in a sandwich bag and seal it. place in a warm dark location. Use the germination time for those seeds. Check after a week to see if any germinated. Count the number of seeds if any germinated. That number will give you the percentage of seeds for that pack, that will germinate.