The starches we think of as “purple sweet potatoes” aren’t all sweet potatoes. And in fact, they’re not all purple.
Throughout Asia—from the Philippines to Japan to Taiwan—purple starches have been kitchen staples for centuries, featured in everything from warm tapioca dessert soups to sausage-flecked curries. While the traditional orange American sweet potato has a headstrong vegetal sweetness that is often bolstered with piles of marshmallows or countered with hearty turkey gravies, many of these purple starches from Asia have a light sweetness that allows the violet-shaded veg to move nimbly between sweet and savory. Though often generically labeled “purple sweet potato” in the United States, roots like taro, yams like ube, and Okinawan sweet potatoes arrive from totally different plants and totally different parts of the globe. And each carries a distinct flavor.
Taro, one of the most popular purple starches, is not particularly purple in hue; the “corm” bulb used most often in taro cooking looks almost like a coconut, mid-brown and downy, and the insides range from pure white to a light lavender. More often, taro-flavored foods and drinks have a little food coloring added for identifying effect. The texture inside is almost chalky, but like all starches, it breaks down through boiling and mashing and is lightly sweet. Taro powders, used sometimes in baking and in taro milk teas, are both sweeter and more purple than the root itself.
Taro, which can be traced back to India and Malaysia, spread north to plant roots in China, Taiwan, Hong Kong, and Japan by about 100 B.C. It serves as a dominant flavor in East Asian baking, boba teas, and as a filling and flavoring in flaky puff pastries and chewy buns—and also as a powdered flavor mix for creamy milk, and steamed in chunks with pork shoulder or fatty Chinese sausages in fried rice flour cakes found on dim sum tables. Sometimes it’s served in a hot coconut milk–based soup with tapioca pearls after meals at Asian restaurants.
Ube is extremely popular in the Philippines and Hawaii and is almost exclusively used in desserts. The flavor is similar to white chocolate or pistachio. Like taro, it is used in powder form for baking or boba. Frozen or fresh ube root is preferred to make the jam-like ube halaya, which can in turn be used to make desserts like doughnuts, halo-halo, and pinwheel ube rolls.
Meanwhile, Okinawan sweet potatoes are the only starch of the bunch that are actually technically sweet potatoes. In Japan, they’re known as beni-imo and have their own KitKat flavor. In Hawaiian cuisine, Okinawan sweet potatoes find their way into “traditional” American sweet potato recipes, like sweet potato pie.
Out of the three, Okinawan sweet potatoes are perhaps the trickiest to ID, since their skin is usually a dusty white or brown, making them harder to tell apart from other varieties of sweet potatoes and yams. But once cracked open, they’re an almost ube-deep purple on the inside. When roasted or steamed whole, they’re gently sweet and crumbly like taro or chestnut, but unlike either taro or ube, Okinawan sweet potato powder, while also useful for baking, has another life as a health food supplement.
Fresh, frozen, and powdered varieties of these purple potatoes tend to be limited to Asian supermarkets. National chains like H Mart, Nijiya Market, and 99 Ranch usually stock some fresh roots and some powders, particularly taro for both, while specialty grocers, like Ing’s Market in Long Beach or Phil-Am Foods, in NYC are a better shot for grabbing ube and Okinawan sweet potato. Meanwhile, you can more conveniently snag powders for all three roots readily on the internet.
Most of the powders are sweeter than their fresh or frozen counterparts, so for those of you looking to add a punch of purple to your next dish, try subbing in taro or Okinawan sweet potato where you would normally use a potato for a savory dish; I’ve found that they especially complement pork in stewed or steamed form. When it comes to desserts, all three are versatile (and vibrant) in baked goods, especially if they’re paired with soft flavors like coconut or vanilla.