Perhaps no part of a plant is as complex or requires such special handling as the roots. But few other parts are so rewarding—and just at the times we need them most. Roots serve a variety of functions. They provide a firm base from which a plant grows upward. They probe downward in search of moisture, collect it and begin the process of sending it up to the leaves, where it’s most needed. In turn, they store the nutrition that the leaves produce.
Although the group that we call “root vegetables” is wide and varied, it’s important to remember that, botanically speaking, not everything that grows underground is a root. True roots include carrots, parsnips and sweet potatoes. But regular starchy potatoes, which grow even deeper under the surface, are tubers. Other vegetables that we consider roots are more technically the junction between the roots and the stem, growing partly aboveground. These include beets, turnips and radishes.
Structurally, though, all of these varied parts are roughly similar. They are all covered with a rough, corky skin, which serves to protect the plant’s interior from damage and retain moisture. That these peels are so spectacularly successful at these jobs is why we can eat root vegetables all winter (although they are usually no longer stored in root cellars). We usually peel this skin before we eat the vegetable. In many cases, because the peel is made of a different material, it is so loosely attached to the root that after cooking, it will slip free of its own accord. In the center of the root is the section that transports water from the earth to the plant’s aboveground parts. This is called the vascular system. It is frequently tough and woody, and in the cases of carrots and parsnips, careful cooks may remove it as well. In between the peel and the vascular system is the part that we really crave. This is the storage system, which is not only tenderer than the vascular system but also where the plant stores the sugars and starches that it will need to grow. (The arrangement is not always so simple. Beets alternate vascular and storage layers, in some cases even colored with different pigments, producing a striped “bull’s-eye” effect.) Root vegetables can be astonishingly sweet. The sugar beet, a cousin of the familiar red beet, is processed to make sugar.
The end result of all of this heavy construction is something that usually looks absolutely unpromising in the raw (“Where did you dig that up?”) but that turns incomparably sweet, flavorful and scented with a little careful cooking. Just when we need these vegetables most, in the bleakest part of the winter, they give us the sustenance to carry on until spring. Their texture and sweetness come from a combination of starches and sugars. To the plant, starches represent food that has been stored for future use, while sugars can be immediately converted to energy. Starches are chemical compounds that resemble tough little pellets when raw. After they are heated in combination with a liquid, they soften. (In this way, what happens when you cook a beet is not all that different from what happens when you make a simple white sauce.)
Sugars are closely related to starches. (Simple and complex carbohydrates, remember?) In fact, enzymes produced by the plant can convert starches (stored food) to sugars (usable food) when doing so is necessary for the plant’s survival. This is why parsnips are almost always sweeter when harvested after a hard frost: the plant, feeling threatened by cold weather, has started converting its stored food to food that it can use immediately. By contrast, a plant such as the carrot, which hails from a more moderate climate, has a higher ratio of sugar to starch and is sweeter right off the bat.
Properly selected and prepared, all root vegetables turn sweet. But this is only part of their appeal. What makes root vegetables so fascinating is the diversity of secondary attributes they possess. In general these fall into two main categories, the sharp and the colorful. The first typifies the flavors of vegetables such as radishes, kohlrabi, rutabagas, turnips and horseradish and comes from varying concentrations of a mustardy sulfurous compound that in nature functions as a defense mechanism. As with onions, cooking tames the heat by altering the enzyme that helps create it, as does pickling in an acid such as vinegar. Pungent as these roots can be in flavor, they are, to varying extents, bland in appearance (although radishes have thin skins that can be colorful).
Other roots, while lacking inner fire, are among the most vibrantly colored members of the vegetable kingdom. The most obvious example is the beet, which, depending on the variety, is colored anything from blood red to golden orange or even pure white. This color comes from the pigment betalain—or its absence. (Betalain also gives bougainvillea its distinctively fiery colors.) Unlike most plant pigments, betalain is water-soluble and will leak readily—as anyone who has cut up beets on a wooden chopping block will sadly attest. For this reason, beets are usually treated differently than other vegetables—cooked whole before they’re peeled. Once cooked, the corky peel will slip right off (although you still have to be careful of staining).
We usually think of carrots as being bright orange, colored with a pigment called, appropriately, carotene. But they, too, come in a wide variety of hues. In fact, the familiar orange carrot probably dates back only to the seventeenth century. Some people believe that the original carrot was a purplish red color nearly identical to that of the beet. These carrots are colored by the pigment lycopene, which is also found in sweet potatoes, as well as in tomatoes, watermelons and pink grapefruits. Other carrots are colored by anthocyanins, pigments that give the reddish color to everything from berries and grapes to autumn leaves. Because all these pigments are so much more colorfast than betalain, the dull corky skin of carrots can be peeled before cooking.
Root vegetables adapt well to both moist- and dry-heat cooking methods. Moist heat, such as that from boiling or steaming, softens the vegetables’ starch and cellulose more quickly and keeps colors brighter and flavors purer and more direct. Dry-heat cooking (primarily roasting) takes longer. The colors tend to be darker and not quite so fresh, and the flavors developed are more complex.
Because of the higher temperatures attained during roasting, the root’s sugars will begin to caramelize, and you will begin to get some of the flavors from browning associated with the Maillard reaction. Most roots can be nicely roasted simply slicked with a little oil. Cooking will be a little faster, and the result a little moister, if the vegetables are wrapped in aluminum foil first. This is absolutely necessary for beets, if for no other reason than to keep them from bleeding all over the kitchen.
WHERE THEY’RE GROWN: Beets are harvested primarily in Wisconsin, New York, Oregon and Texas.
HOW TO CHOOSE: Beets are usually sold with their tops on. Inspect the greens for freshness. Also, avoid any beets with cracks or soft spots or that have a lot of hairy secondary roots.
HOW TO STORE: Store beets in a plastic bag in the refrigerator.
HOW TO PREPARE: Beets will bleed pigment all over everything. Don’t peel them until after they’ve been cooked; they will keep their color better. Also, leave about an inch of tops on and don’t break off the bottom root for the same reason.
ONE SIMPLE DISH: Wrap beets in aluminum foil and roast at 400 degrees until they are soft enough to be pierced with a knife, about 1 hour. Peel them, quarter them and dress them with olive oil and red wine vinegar. Season with salt to taste and finish with a generous grinding of pepper.
WHERE THEY’RE GROWN: California grows more than two thirds of the carrots that are harvested in the United States. California also leads in parsnip production.
HOW TO CHOOSE: Carrots and parsnips with the tops on are great because you can tell from the greens how recently they were harvested. But sometimes very fresh vegetables are sold without the tops. The best trick is to pay attention to the intensity of the color. The pigments fade with time, so the deeper orange a carrot is, the more likely that it’s fresh. Avoid vegetables with splits and cracks and those with lots of little hairy roots; they are too old.
HOW TO STORE: Store carrots and parsnips in a plastic bag in the refrigerator. Remove the tops if you’re not going to be eating them right away, as the greens will pull moisture from the roots.
HOW TO PREPARE: Carrots and parsnips should almost always be peeled. The peel is corky and cooks to a different consistency than the core. Also, if they have a large, pale center, quarter them lengthwise and cut it out. It will be woody and flavorless.
ONE SIMPLE DISH: Carrots and parsnips are delicious braised. Peel them and slice them into rounds or sticks. Place them in a skillet with enough water just to cover the bottom of the pan and a knob of butter (and maybe a hint of minced garlic or shallots). Cook, covered, over medium heat until almost tender, then remove the lid, increase the heat to high and cook until the liquid evaporates.
WHERE THEY’RE GROWN: Florida grows more than half the radishes produced in the United States, followed by California, Michigan and Ohio.
HOW TO CHOOSE: Radishes are almost always sold with their tops. That’s the first thing to check—they should be bright green and not at all wilted. The roots should be brightly colored and free from cracks and nicks. Give them a squeeze: if they’re not hard, they could have a soft center.
HOW TO STORE: Store radishes in a plastic bag in the refrigerator, removing the tops if you’re not going to use the radishes right away.
HOW TO PREPARE: Radishes need only a thorough washing to be ready to eat. Don’t skip this step, though. Because they’re grown in fine, sandy soil, grit can show up even where it’s not obvious.
ONE SIMPLE DISH: Wash radishes in ice water, then arrange them on a plate around a crock of softened butter and a bowl of coarse salt. To eat, rub them in the butter, then dip them in the salt.
WHERE THEY’RE GROWN: North Carolina is the leading state for sweet potatoes, followed by California, Louisiana and Mississippi.
HOW TO CHOOSE: There are two kinds of sweet potatoes in markets. One is pale orange and starchy; the other is dark orange, a little sweeter and very moist. Sweet potatoes are frequently called “yams,” although they are completely different from true yams, which hail from West Africa. Use the dark orange ones when you want the sweet potato to hold together in a dish. Use the pale ones when you want a dish to be light and fluffy.
HOW TO STORE: Sweet potatoes will last for a couple of weeks at cool room temperature, but refrigerating does them no harm.
HOW TO PREPARE: Sweet potatoes need only to be peeled before cooking. If you are going to roast them, even that isn’t necessary—you can spoon the pulp from the skin after they are cooked.
ONE SIMPLE DISH: Pierce sweet potatoes with a fork in several places. Place them on a jelly-roll pan and bake at 450 degrees until they are quite soft, 30–40 minutes. (Piercing keeps them from exploding, and the jelly-roll pan will catch the sugar syrup they exude.) Spoon the pulp from the skin and beat it with a couple of tablespoons of butter, a little salt and a grating of nutmeg.
WHERE THEY’RE GROWN: Farmers in two different areas of the United States grow turnips. Tops are farmed in the mid-South, primarily in North Carolina and Georgia. Bottoms are grown in California. Illinois grows both tops and bottoms. Rutabagas, which are a cross between turnips and a kind of cabbage, are too sparsely grown to be tracked statistically.
HOW TO CHOOSE: Choose roots that are free from nicks and scars. Check the top of each turnip or rutabaga, where the greens once were. As the roots sit, they will continue to sprout new greens, which the produce manager will trim. The more the tops have been trimmed, the older the root probably is. In Japanese markets you can find small white turnips that have the tops attached. These are milder and sweeter than other turnips.
HOW TO STORE: Store turnips and rutabagas in a plastic bag in the refrigerator.
HOW TO PREPARE: Turnips and rutabagas should be peeled, except for the small Japanese varieties, which have such a thin skin.
ONE SIMPLE DISH: Braise turnips or rutabagas just as you would carrots (see above).