Sinkers Grow, Floaters Don't

Before you throw away those seeds you've had for a while test their viability. Fill a bowl with water, add the seeds and let it sit overnight. In the morning skim off the floaters - these seeds won't grow. Pour the water through a fine sieve and plant the seeds that are left. These are the sinkers, and these seeds will grow. The "best before" date on the packet is just an indication, so before you toss, test.