Beets are notable for their sweetness--they have the highest sugar content of any vegetable, but they are very low in calories. Their sweet flavor comes through whether the beets are fresh or canned (which is the way most beets are sold in the U.S.). Unlike many other processed vegetables, canned beets are perfectly acceptable in both taste and texture; if not pickled, their sweet flavor is largely unaffected by the canning process. Fresh beets, however, have twice the folate (folic acid) and potassium, and have a distinctive flavor and a crisp texture not found in canned beets. Fresh beets also supply a nutritional bonus--their green tops are an excellent source of beta-carotene, calcium, and iron. The beets we eat as a vegetable (also called red beets, root beets, and table beets) are a root vegetable with two parts, the root and the edible green leaves. They belong to the botanical species Beta vulgaris, which also includes sugar beets (which are processed for sugar), mangel-wurzels (very large bulbs used as animal fodder), foliage beets, and Swiss chard (the latter two grown for their greens, not their roots). All these vegetables are descended from a wild slender-rooted plant that grew abundantly in southern Europe. In ancient civilizations, only the green leaves of the beet plant were eaten; the roots--which did not look like modern beets--were used medicinally to treat headaches and toothaches. Beets with good-sized, rounded roots, like those we eat today, were probably developed in the sixteenth century, though it took another 200 years before they gained any popularity as a food. Varieties The beets generally seen in the market are globe-shaped roots, with deep red flesh and green leaves that have either green or red veins. Other less common varieties have golden or white flesh, but these are mainly raised by local growers and home gardeners. Availability Fresh beets are always in good supply. They are grown in more than 30 states, and crops are harvested and shipped throughout the year. June through October, however, are peak months, and at the start of the season you can find young beets with small tender roots that are suitable for cooking whole. The roots get larger--and tougher--as the season goes on. In the off-peak months, you may also find "clip-topped" beets that have been in storage, but these are less tender than freshly harvested beets.