Store hemp seeds cool, dark, dry, and well sealed. Whole hemp seeds (hemp grain) keep for a year or more in a sealed jar or bag in a cupboard, and longer in the refrigerator. Hemp hearts (hulled seeds) have lost their protective shell, so keep them in the refrigerator or a climate-controlled space to slow oxidation and rancidity.
The best way to store hemp seeds is cool, dark, dry, and well sealed. Those four rules cover almost everything, and the reason behind them is the oil.
Roughly a third of a hemp seed by weight is oil, and about three quarters of that oil is polyunsaturated fat, mostly linoleic and alpha-linolenic acid. Polyunsaturated fats are exactly the kind that react with oxygen, and heat and light speed that reaction up. Once the oil oxidizes the seed tastes bitter and smells like old paint, and the nutrition you bought it for is largely gone.
How long your seeds last also depends on which kind you have. Whole hemp seeds, also sold as hemp grain, still have their hard outer shell. Hemp hearts are the same seed with the shell removed. The shell is the difference between a pantry item and a refrigerator item.
The shell protects the kernel from air and light, so whole seeds are forgiving. A cupboard or any climate-controlled room is fine as long as the seeds are in a sealed container such as a zip-top bag or a mason jar. They will last longer still in the refrigerator, so if you have the space, use it.
Keep them away from heat, sunlight, and movement. Movement matters more than people expect: shaking, pouring, and rough handling crack the seed coat, and every cracked seed is a seed that oxidizes. Hemp processors grade grain partly on peroxide value, a measure of rancidity, and the Alberta hemp harvest guidelines note that most of that damage comes from mechanical injury during handling.
If you are storing grain in bulk, moisture is the other number to watch. Farm guidance from Alberta Agriculture puts safe storage below 9 percent moisture, with many processors requiring 8 percent, and the ASTM D8465-23 storage guide for producers targets 5 to 9 percent. Wet or heated grain will go rancid no matter how well it is sealed.
Hemp hearts have lost their protective shell, so the oily kernel sits in direct contact with air. They oxidize faster and go rancid sooner. Store them in the refrigerator or a climate-controlled environment in a sealed container, and put an opened bag in the fridge as soon as you get it home. For long-term storage the freezer works well and does not harm texture or flavor.
Viable seed follows the same rules, but the research is more specific. A five-year storage study by Small and Brookes found that hemp seed held at 11 percent moisture and room temperature lost all germination in under 18 months. Either cooling the seed to 5 degrees Celsius, roughly refrigerator temperature, or drying it to about 6 percent moisture preserved viability for years, and doing both helped a little more.
The rule of thumb is simple. Shell on, a sealed jar in the cupboard is fine and the fridge is better. Shell off, the fridge is the cupboard.