Steaming is a quick, healthy way to prepare vegetables. According to science and health writer Rachael Moeller Gorman, steaming vegetables preserves nutrients because they are not in direct contact with water, which leeches out vitamins. In addition to the health benefits of steaming, it also allows you a considerable measure of control over how long your vegetables cook and how firm or tender they are.
In general, the denser the vegetable, the longer you need to steam it. In addition, smaller chunks steam faster than larger ones. Assuming that your vegetables are cut in 1-inch squares, it takes 8 to 10 minutes to steam hard root vegetables such as beets, potatoes, carrots, turnips and rutabagas. Softer vegetables with higher water contents, such as zucchini and peppers, can take as little as two to three minutes. Medium-hard vegetables such as broccoli and cauliflower will steam until they are tender in three to five minutes.
Leafy greens tend to steam more quickly than do solid vegetables, but there is still considerable variation in cooking times depending on which type of leafy green you are using. Spinach will cook in barely a minute, and chard takes about two minutes. Collard greens take three to five minutes, and the tougher types of kale, such as curly green kale, can take six to eight minutes.
Color is an important indicator of when you are done steaming your vegetables. The color of most vegetables, such as broccoli, green beans and carrots, becomes deeper and brighter as they approach the ideal level of doneness. Vegetables tend to grow grayer and less colorful when you cook them too long. When judging doneness based on color, figure in whether you will be serving your vegetables right away or whether they will sit for a while before you serve them. Vegetables tend to continue cooking as they sit, so if you are not serving them right away, it is best to undercook them a bit, which involves turning off the heat as soon as their color starts to deepen and brighten.
As with so many other cooking techniques, the ideal amount of time for steaming vegetables depends on how firm or tender you like them. If you like your vegetables very soft, then cook them longer; if you like them firm and chewy, cook them for less time. Learning about steaming times also involves learning about your personal preferences and paying close attention as you steam your vegetables to discern the ideal level of doneness for you.