There are over 4,000 types of potatoes in the world, and they can all be classified into three categories: floury, all-purpose and waxy. Floury potatoes are high in starch and good for mashing or baking. All-purpose potatoes are medium in starch levels and can be used as either floury or waxy potatoes. Waxy potatoes are relatively low in starch and ideal for use in salads. They hold their shape well when boiled or roasted.
This type of waxy potato is small -- usually 5 to 10 cm (2 to 4 inches) in length, narrow, and elongated, resembling a finger. Fingerling potatoes can be a variety of colours, from red to purplish-pink to yellow. Fingerlings cook more quickly than larger potatoes, maintain their shape well when cooking, and generally are aesthetically pleasing on a plate.
Red potatoes, also known as red jacket potatoes, are medium-sized waxy potatoes with white flesh and red skins (or jackets). Red potatoes are often sold "new," or immature. As mature potatoes, they are low in starch and are a top choice for boiling. Red rounds are the most common waxy red potato.
White round potatoes
White round potatoes contain medium to low starch levels, so they can be classified as either waxy potatoes or all-purpose potatoes. These potatoes maintain their shape when boiled or roasted, and are also ideal for mashing or baking. Some types of white potatoes include Saxon and Cara potatoes.
Yellow potatoes, such as the Yukon Gold, can also be classified as either waxy potatoes or all-purpose potatoes. Like white round potatoes, yellow potatoes typically maintain their shape when roasted or boiled, and can also be used to make mashed or baked potatoes.
The term "new potatoes" technically refers to any immature potato harvested in spring or early summer, but is often used to describe all small waxy potatoes. New potatoes can be distinguished from fully mature potatoes by their flimsy skins which can be peeled off using just fingers. They are ideal for boiling or roasting, as they maintain their shape particularly well when cooked whole.
Some potatoes fall into the all-purpose category rather than either the "waxy" or "floury/mealy" category. All-purpose potatoes have medium starch levels and are good for baking, mashing, and boiling. They maintain their shape when boiled better than floury potatoes but not as well as waxy potatoes. These include Yellow Finnish and Peruvian Blue potatoes.