Asparagus, spinach and scallions are best in the spring. Many vegetables, like tomatoes, squash and Swiss chard are good in the summer. Root vegetables like acorn or butternut squash bring warmth to any autumn table. And if you live in a warm climate, you can explore options of cultivating your own vegetable gardens to get the most selection based on your tastes. Burying vegetables in butter, preparing them with animal fat or dousing them in oil adds many extra calories without adding nutritional value. Try steaming or roasting with a little bit of olive oil for nutritious and delicious preparations. Even though too much fat is not beneficial, adding some plant-based fats like olive or walnut oil to your deep greens (like leafy greens, broccoli and Brussels sprouts) actually helps your body absorb more of their nutrients. Freezing vegetables in season and storing them for future use is an easy way to get the flavor of the harvest all year round. For quick dishes, choose frozen, pre-chopped organic vegetables from your grocery store.

TL;DR in Chinese:
购买应季的新鲜蔬菜。 烹饪蔬菜时选用健康的烹饪方法。 冷冻蔬菜也是一种选择。