Flaxseed can be sensitive to heat and sunlight and has a reputation of spoiling quickly. It’s best to store your whole flaxseed in the refrigerator to keep it fresh longer. If you grind your own flaxseed, keep the seeds in the fridge and take them out just before you are ready to grind them. Then store the ground flaxseed in an airtight container, where it should stay fresh for a few months.