Popeye’s favorite food is one of the best cold-weather crops a gardener could ask for. Four to six weeks before the last frost date in your area, you'll need to kick things off by following a process called priming: Soak some seeds in water for 24 hours. Take them out and let them dry off on a paper towel for a day or two, then seal the seeds in an airtight zip-lock bag and keep them in a cool room for up to one week. When their week-long stint in a cool room is up, sow the seeds in an inch of tilled soil that has a temperature below 70°F. You can start harvesting your spinach leaves whenever they reach the desired size.