While it's possible to buy just about any fruit or vegetable whether it's in season or not, it's more economical to buy them when they are in season. They taste better as well. When it's winter, and cold, in most of the United States it's warm in South America. Fruits and vegetables are grown there, picked unripe, and shipped to the states. For fresher and tastier produce, stick with local seasonal fruits and vegetables.
Early spring sees asparagus and rhubarb first hitting the market. Asparagus are harvested before the leaves have begun to unfold. They come in green and white. The white version is simply asparagus that has been covered from the sun so the stem doesn't turn green. Rhubarb is considered a fruit because it is used mostly in desserts. Only the bright red and pink stems of the plant are edible. The rest is toxic. You might not think of oranges as a spring fruit, but that's when Valencia oranges naturally ripen in Florida, California and Arizona.
Late spring harvest includes cool season crops like peas, broccoli and cauliflower that were planted in early spring, right after the last frost. They stop producing well when warm weather hits. Some leafy greens, such as chard and kale, keep producing all summer long. Lettuces and spinach, start to bolt, or throw up flower stalks, when the weather warms up and should be harvested long before that, because as soon as the stalk starts, the greens become bitter.
Summer is when fruits and vegetables are most bountiful. Fruits such as peaches, apricots and cherries reach their peak of ripeness in summer. Summer berries include raspberries, blackberries, blueberries and, of course, strawberries. Melons need the heat and long days of warmth to do well, so grow best in the summer and include honeydew, cantaloupe and watermelon. Summer vegetables include beans, tomatoes, corn, peppers, squashes and eggplant.
Apples announce autumn, loud and clear, even though some varieties ripen in late summer. Other fall fruits include pears, persimmons and grapes. Vegetables include cabbage, mostly because it has such a long maturity time and won't be at full size before fall. Brussels sprouts taste sweeter if they've been exposed to a light frost in the fall. They too have a long time to harvest. Endive, grown commercially, is grown in greenhouses so it can be shielded from the sun and kept white. When grown in a garden, it is ready in fall.
Root vegetables may be left in the ground during the early part of the winter, before the ground freezes solid. These include carrots, turnips, parsnips and rutabagas. Once the ground freezes, the roots do too, so bring them inside before that happens. Other vegetables are considered winter vegetables because they're starchy, such as potatoes, and will keep well in a cold but not freezing place. Winter squashes such as acorn and Hubbard have thick hard skins that prolong the life of the squash after it's been picked. Like summer squashes such as zucchini and patty pan, winter squashes are grown during the summer.