California grows a vast majority of the fruits and vegetables we consume in the United States. Some stats put California at growing as much as 80% of all produce! And though we usually see most fruits and vegetables available at the market year round, it doesn't mean they are at their freshest or at their peak nutritional content. Some produce does get shipped in from other countries located in a different hemisphere, but other produce can sometimes be stored in freezers to be sold at markets later.
Studies have shown that the when we pick fruits and vegetables and the time between harvesting to eating can effect the fruit and vegetables' nutritional content. For example, tomatoes prematurely picked before ripening are found to have less vitamin C than tomatoes picked at peak ripeness. Also, fruits and vegetables start to lose their nutritional content as soon as they are picked. Natural processes and compounds like respiration and enzymes start breaking down our produce and releasing nutrients quickly. Some fruits and vegetables decay sooner than others but the process happens to all of them. We can tell when our produce starts to change in color, texture, and taste.
Nutritionists will suggest for you to get your produce locally and while it's in season. The less time it has to travel from farm to table, the better. It's going to have more of its nutrients in tact. Plus, get your fruits and veggies when they're in season! Below is a quick cheatsheet for different fruit and vegetable seasons. The actual harvest and availability dates change about a week or two from year to year but the general seasons usually stay consistent. If you're ever unsure, check with a grower at your local farmers market or a produce expert at your local supermarket. And again, some produce have overlapping seasons or simply last longer after harvest, so don't be surprised to see some produce show up in more than one season. Another huge benefit of eating fruits and vegetables in season is that your kitchen's menu keeps changing and gets more creative. There can be a new group of veggies and fruits featured each month. Cheers to your health!
Please keep in mind that this list is not 100% complete. It's just a few common fruits and vegetables to keep in mind.
Here's more to read and a few more cheatsheets: