The Idaho Center for Potato Research and Education is a virtual center made up of faculty and staff located at the University of Idaho campus, four research and education centers, and numerous county extension offices.


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Frequently Asked Questions



What is a U.S. No. 1 potato?


Grade standards are use to ensure that the customer is provided with a uniform, quality product. Potatoes classified U.S. No. 1 must meet certain quality standards established by the United States Department of Agriculture-Agricultural Marketing Service. Potato tubers must meet a minimum size requirement, either a minimum weight or minimum diameter. Some other requirements of a U.S. No. 1 potato include being "fairly well shaped, firm, and free from freezing, blackheart, and soft rot and wet breakdown."


Do we eat the roots of potatoes?


Potatoes are occasionally referred to as a root crop because we eat a part of the plant that grows underground. However, the part of the potato that is eaten is not a root, it is actually a specialized stem called a tuber.


What causes green tubers, and are they safe to eat?


Potato tubers are specialized stems of a potato plant, and tubers that are exposed to light, will naturally turn green. The green is nothing more than chlorophyll, a harmless compound found in all green plants. However, when potato tubers turn green there is usually an increase in a glycoalkoloid compound called solanine. Tubers with a high concentration of solanine will taste bitter, and can be harmful if eaten in large quantities. To be safe, it is best to not eat green tubers. Consequently, it is important to store potatoes in the absence of light to prevent greening.


What is the hole in the center of a potato?


You may occasionally cut a potato open to find a dark-colored hole, most often near the center. This hole is a naturally occurring physiological disorder called "hollow heart" caused by environmental stresses such as cold and wet soil conditions occurring in the field while the potatoes were growing. If all you are concerned about is a hole in the potato, there is absolutely nothing wrong with the potato and it is definitely safe to eat.


What is the "black soil" on the potato skin that is difficult to wash off ?


When washing potato tubers you may some times encounter black material that looks like soil, but is difficult to wash off. This black material is commonly called "black scurf." Black scurf is a fungus that was looking for a place to spend the winter so grew on the outside of a potato tuber. This fungus is not harmful to people. It is completely safe to eat the tubers even if you cannot remove all the black material on the tuber skin.


Can I grow potato plants by planting seed pieces cut from tubers purchased in a grocery store ?


Potatoes purchased in a grocery store will not grow plants because the tubers have gone through a process that prevents them from producing sprouts, and eventually a plant. It is best to buy certified potato seed tubers from your local nursery retailer. Buying seed from a nursery will help ensure that you will have healthy potato plants in your garden.


What is the difference between a potato and a sweet potato?


The only common thing between potato and sweet potato is the word "potato." Potatoes that are used for baking, French fries, boiling, etc. are some times referred to as Irish potatoes. Potatoes belong to the Solanaceae (nightshade) plant family that also includes tomatoes and eggplant. The scientific name of potatoes is Solanum tuberosum. The part of the potato that we eat is a tuber, which is a specialized stem.


Potatoes are grown in every state in the U.S. although the crop is harvested various months of the year.

Sweet potatoes belong to the Convolvulaceae (morning glory) plant family, and the scientific name is Ipomoea batatas. It requires relatively warm growing conditions such as found in North Carolina, Louisiana, and Mississippi. The edible part of the sweet potato is a storage root, which has a sweet taste.


What is the difference among red, white, russet potatoes?


The obvious difference among red, white, and russet potatoes is the skin color. Russet potatoes are brown, although the term "russet" does not refer to the color, per se. The term "russet" refers to the "net-like" appearance of the tuber skin. The primary difference in these three types of potatoes is the intended use. Potatoes with red skin are generally used for boiling and mashing because the tuber flesh does not readily break apart when boiled. Round, white potatoes are most commonly used to make chips because the tubers have a relatively high percentage of dry matter (low percentage of water). However, other white-skinned varieties can be used for other purposes. Russet-skinned potatoes are used for all purposes except making potato chips. Although potatoes were developed for a particular purpose, you can still use one type of potato for most any purpose, but the quality of the end product may be inferior.