There are many perennial vegetables available to gardeners, but many are not well-known, or are grown as annuals. Perennial food plants can save time and money, as seed does not have to be purchased and planted each year. Because their root systems are well-established and they often leaf out early in the year, perennial plants can require less weeding and watering than annuals. Like asparagus, some are available earlier (or later) in the season than annual plants, and many of them can also function as attractive ornamentals. And because the soil does not need to be tilled each year, its quality is not eroded over time.
Some commonly grown, edible, and hardy perennials include asparagus, chicory and dandelion, watercress, daylily, rhubarb and sorrel. Other vegetables are only perennial in warm climates, such as tomatoes, peppers, eggplants, taro, globe artichokes, New Zealand spinach, malabar spinach, perennial brassicas, chayote, runner beans, edible hibiscus, breadfruit, and bamboo. Some could be grown as perennials but are generally harvested and replanted each year, such as potatoes, sunchokes, multiplier onions and arrowhead. Still others are simply not well known or not commonly eaten, such as skirret, water celery, ostrich fern, giant Solomon's seal, good king Henry and linden. And some are poisonous, foul-tasting or will sting you unless they are prepared in the right way at the right stage of growth, such as stinging nettle, udo and pokeweed.
If you are interested in growing some less well-known perennial vegetables, always be sure that you are growing the correct plant (by checking the Latin name) and that you are correctly preparing the right part of the plant, harvested at the right time. A good reference is Eric Toensmeier's excellent book Perennial Vegetables, which includes information on a wide variety of plants, including how to eat them.