Knowing what fruits and vegetables are in season can be confusing—especially when your local grocery store is stocked and loaded with every kind of produce under the sun at all times. If you don’t get the hoopla surrounding farmer's markets, it may help to know that in-season produce isn’t just more flavorful than what's shipped across the country, it’s more nutritious, too.

Fruits and vegetables harvested at just the right time in their peak season are more nutritionally dense because they’ve had time to mature and develop abundant nutrients. Sure, that grapefruit (a winter fruit) you eat every morning year-round tastes fine—since it was picked prematurely to ripen over the days- or week-long journey to your supermarket—but it isn’t giving your body its full potential of vitamins and nutrients. Take spinach, for example. Eating it in-season provides up to three times more vitamin C than eating it out of season, according to the Cleveland Clinic.

To determine the most nutritionally dense summer fruits and vegetables, we went to Adam Kelinson, a private chef and nutritional consultant for athletes, executives, and celebrities (the likes of Prince and Hillary Swank), and author of The Athletes Plate: Real Food for High Performance. Take this list with you the next time you head to the grocery store or farmer's market, and enjoy the freshest, healthiest produce the summer has to offer.