Potatoes are so embedded in North American culinary culture that it's funny to realize they weren't even cultivated here until the 19th century. They're native to the Andean mountains in South America, where Spanish explorers first encountered them in the 16th century and then brought them back to Europe. Potatoes actually made their way to the US and Canada not directly from South America, but through a more circuitous route, arriving with Irish immigrants to the US in the mid-1800s. Before that, potatoes had already made their way to India, China, and Japan in the 17th century, and in the 19th century, European missionaries and colonists spread their cultivation to East Africa. Adaptable to various climates, capable of relatively high yields, and easy to store for long periods of time, potatoes have flourished all over the globe. Today, they are the most popular vegetable in the world.
There are roughly 4,000 different varieties of potatoes worldwide, most of which are found only in the Andes, not in your local supermarket. These starchy tubers, which belong to the nightshade family (along with eggplant, tomatoes, and peppers), have a reputation as a comfort food, not a health food. But potatoes are actually pretty nutritious, with more potassium than bananas and high levels of vitamin C—sailors once ate them to prevent scurvy. They're also rich in vitamin B6, zinc, and iron.
No matter what kind of potato you're buying, look for one that has tight, unwrinkled skin. Avoid sprouts, green coloration, and soft spots or other signs of rotting. Before going to market, all mature potatoes are dried and then cured, which means they're stored for about two weeks at 60 to 70°F (16 to 21°C) and high humidity to heal any surface injuries. After curing, they can be stored in a dark, dry, and cool place for a couple months. The exception here is new potatoes: Freshly picked and thin-skinned, these young potatoes are sold uncured and should be eaten within a few days of purchasing. For mature potatoes, the ideal temperature for storing is around cellar temperature. But, since very few people have root cellars anymore, if you're storing potatoes for longer than one or two weeks, keep them in a basement, pantry, or dark and cool closet or cabinet. Do not keep them in the refrigerator—at about 40°F (4°C) or cooler, their starches will begin to convert to sugars. They also shouldn't be stored near onions; moisture and gases released by both vegetables can accelerate degradation in each.
Of course, potatoes have an incredible range of culinary uses: Beyond deep-frying them and incorporating them into butter-soaked mashes, they can be boiled, baked, roasted, steamed, grilled, pan-fried, or sautéed; they can star in salads or play a supporting role; and they can add body to soups and stews. Choosing which potato is best for a certain dish mostly depends on the level of starch and moisture you need. Potatoes are generally divided into three categories: high-starch (including Russet Burbanks, the classic baking potatoes); low-starch (a.k.a. waxy), like Red Bliss; and medium-starch, like Yukon Golds.
As Kenji has explained in his investigation on ultra-fluffy versus rich and creamy mashed potatoes, starch molecules are bundled in the cell walls of potatoes, and those cells are held together by pectin, the way spackle holds together bricks. When potatoes are cooked and mashed, the pectin breaks down, and the cells expand and separate, releasing the bundles of starch molecules. Those bundles will absorb water until they burst, releasing the starch molecules, which can help thicken a dish and act as a binder.
If there's an overabundance of starch, of course, a dish can be thickened too much and turn gluey, the classic mashed-potato fail. The key is getting the right amount of starchiness—a balance between how much starch is in the potatoes and how much you're working it to release those starch molecules. Waxy potatoes won't help much as thickeners (due to their low starch content), and they also don't brown as readily as starchy potatoes (thanks to their high moisture level), but they will hold their shape well during cooking. So thinking about your priorities for the dish—whether you want the potato in it to keep its structural integrity, break down and act as a binder, or get super brown and crispy—will help you figure out whether you want a low-starch or high-starch potato, or something in between.
Unfortunately, potatoes aren't labeled by moisture and starch content at the supermarket, but it's relatively easy to remember where they fall on the starch spectrum. Here are the most common varieties and what they're best suited for.
The good ol' white- or yellow-fleshed Russet Burbank (also known as Idaho), with its rough, ruddy skin and mild flavor, is an American favorite for good reason. Low in moisture and high in starch, the russet's dry, floury texture makes it ideal for preparations in which lightness is the goal. Russets' cells break down easily, so they don't have to be cooked too long or mashed too thoroughly to take on a smooth consistency. Less smashing means that fewer starch granules—which form a more gluey texture en masse—are burst, producing the fluffiest mashed potatoes, an airy skordalia (Greek garlic-and-potato dip), and light and tender gnocchi. Because they have less moisture than waxy varieties like Red Bliss, they also crisp up more easily, making them perfect for potato hash and McDonald's-style French fries, and they readily soak up other ingredients, so they're the natural choice for a classic baked potato. Russets' starchiness is also key to thickening some soups, such as this potato-leek soup.
Medium-Starch (All-Purpose) Potatoes
In 1980, the smooth-skinned, yellow-fleshed Yukon Gold was developed in Canada by crossing a North American white potato with a wild South American yellow one. It splits the difference between dry, fluffy russets and denser, waxier varieties like Red Bliss, making it extra versatile. If you want crispy roast potatoes with tender, flavorful interiors; ridiculously rich and creamy mashed potatoes; or extra-silky pommes aligot, the Alpine cheese-laced mashed-potato dish, Yukon Golds are the ideal choice.
The trick to achieving creaminess while avoiding glueyness is to release some of the starch, but not too much. That's why subjecting Yukon Golds to the whirling blade of a food processor can result in a pasty mess, but using a ricer to break the potatoes and their starches down just enough yields a creamy mash. That denser, creamier texture also works nicely in dishes, like tortilla española, for which you want the potatoes to keep their structural integrity—a starchier type of potato will disintegrate more readily. Yukon Golds can be swapped for other yellow potatoes, like Yellow Finns, German Butterballs, and Alby's Gold potatoes.
Purple and Blue Potatoes
There are many different kinds of both blue (e.g., Adirondack Blue, All Blue, and Russian Blue) and purple potatoes (e.g., Purple Majesty, Purple Viking, and Purple Peruvian), and all of them are heirloom varieties. Typically, both purple and blue potatoes are medium-starchy and work well in some of the most common preparations for potatoes: roasting, potato salads, and mashes. They bring a healthy dose of antioxidants in the form of anthocyanins, a type of flavonoid also found in blueberries, which give them their unusual color.
There are two kinds of white potatoes: round, which includes Atlantics and Kennebecs (also known as Maine potatoes), and long, like Long White potatoes (also known as California Whites). Both are thin-skinned and have a medium to low starch content, though the round ones usually have waxier flesh. They're a serviceable all-purpose potato, and well suited to gratins, salads, and braises, but they don't tend to brown well, and we usually prefer other varieties for most preparations.
Low-Starch (Waxy) Potatoes
In addition to russets and Yukon Golds, the waxy, creamy Red Bliss is one of the most recognizable among supermarket varieties. (Other, less common red potatoes include the all-purpose Red Gold and Norland Red.) Red potatoes' low starch content means they don't work as well in dishes that need a little natural binder, like creamy mashed potatoes, or ones where you want to get some crispy surfaces. But if you need a potato that doesn't crumble and leach starches, Red Bliss should be your go-to, particularly for a clambake or German potato salad. They're also a good substitute for new potatoes when you can't find those in the market.
While names like Yukon Gold and Russet Burbank refer to particular varieties of potatoes, "new potatoes" are literally just that: young potatoes. They're harvested while the potato plant leaves are still green, between November and June, while mature potatoes are harvested when the plants' tops have turned brown. No matter the variety, new potatoes have thin, delicate skin and moist, sweet flesh, and they can be used interchangeably with red potatoes. (Smaller red potatoes are sometimes mislabeled as new potatoes; a true new potato's skin will come off if you scratch it with a fingernail.) In contrast with mature potatoes, which will keep for a few weeks, new potatoes should be used within a few days of buying.
One of the advantages of the smaller new potatoes is their great skin-to-flesh ratio, which is nice for dishes like Colombian-style salt-crusted new potatoes and home fries. And, because the skins are so thin, you can bake them without peeling them, which makes them a good candidate for salads, like a classic Niçoise salad, and casseroles, such as this cheesy onion and potato gratin.
Like new potatoes, long, skinny fingerlings aren't any particular variety. Russian Banana is a common one you might see at the farmers market; others include French, La Ratte, Rose Finn Apple, and Ruby Crescent. Also like new potatoes, their skin is so thin that they don't require peeling, and they're typically small enough that you don't need to cut them up, either. We like them in salads, like this potato salad with creamy dill dressing, or a kale salad with marinated mushrooms.
The sweet potato (Ipomoea batata) is not closely related to the potato botanically, but it's often prepared in similar ways. The most common varieties of sweet potatoes in the US are the sweeter Beauregard (the most widely grown cultivar), the slightly sweet Jewel, and the mild Garnet (also known as red yam). There are also white- and yellow-fleshed varieties, including drier, not-so-sweet Cuban or Caribbean sweet potatoes, also known as boniatos, and ultra-sweet Japanese sweet potatoes, known as satsumaimo in Japan, where they are roasted over coals and sold whole in markets.
Like true potatoes, sweet potatoes are very good roasted and mashed. Thanks to an enzyme that attacks starches, sweet potatoes will actually get sweeter at temperatures between 135 and 170°F (57 and 77°C), much lower than the typical roasting temperature. For that reason, we like to par-cook sweet potatoes before higher-heat cooking, either by putting them in a cool oven and letting them heat up at a low temperature while the oven preheats, or by cooking them gently in water before roasting them.
Perplexingly, many classic preparations load them up with even more sugary ingredients, like maple syrup and marshmallows, but they offer plenty of sweetness all on their own and do well with contrasting flavors, as in this recipe for miso-scallion roasted sweet potatoes, or complementary flavors, as in this smoky spiced-pecan variation. Of course, their sweetness also makes them a natural candidate for desserts, most notably an old-fashioned sweet potato pie.