Potato Science

By Eve Pranis, June 23, 2008

Most grocery-store potatoes are treated with a chemical that inhibits their sprouting and spoiling. If you want to find potatoes to grow in the classroom, look for those that have already begun to sprout. Try keeping some in a warm area to encourage sprouting or ask at the grocery store for older unsold potatoes that have begun to sprout. You can also get designated "seed potatoes" through a seed catalog or at a local garden center. Once you have your tubers in hand, try some of these activities:

Spud Growing Challenge

While we hear from many classes who have raised lettuce, tomatoes, beans, and other vegetables indoors, we've only heard from a few who have actually harvested spuds from containers in the classroom. Teacher Carol Anne Margolis from Smithville, NJ, claims that her kids have reaped a potato harvest from one- or two-gallon containers on a sunny windowsill and in a GrowLab.

Put your potato passions to work and see if you, too, can generate some spuds indoors. (Keep in mind that new tubers will grow above the original piece planted, so plant the piece a couple inches deep, then continue to cover new shoots with soil as the plant matures.)

Then e-mail us the type of container used, the growing medium used, the types of potatoes used, how you treated the seed pieces, and where in the classroom you located them (in a GrowLab? On a windowsill?). Include a drawing or photo and description of your harvest, including the number, size, and weight of potatoes produced. We may feature your story on this site!

Tubers vs. Seeds

Try growing and comparing potato plants both from tubers and true seeds. Have students predict what the differences in the plant' appearances, growth rates, and so on might be, and discuss the implications of each method for farmers and gardeners. (For a suggested lesson plan, see "The Eyes Have It" activity from GrowLab: Activities for Growing Minds, available in the Kidsgardening Store.)

How Small Can You Go (and Grow)?

Conduct an investigation to discover the smallest piece of potato that, when planted will produce a new potato plant (It's rumored that poor farmers have started new plants from mere potato peelings containing eyes!) Or determine whether the size of a seed potato piece affects the size of the plant.


Use a sprouting potato to investigate the concept of phototropism. Have students create mazes from shoe boxes and cardboard scraps to discover whether potato sprouts will actually seek light.

Stalking Starch

To test for the presence of starch, cut a potato in half and brush iodine on the cut half. Iodine turns dark blue/black in the presence of starch. By observing, can students tell where the starch is concentrated in the potato? (Most starch is stored inside the protective skin, while the center is mainly water.) Invite students to bring in other foods they think may contain starch, make predictions, and test them too.

Try sprouting and growing a potato for a few weeks, then test for iodine again. Can students explain their findings? (Most of the starch will have been removed from the potato piece to provide nutrients for the young plant.)

Going to Seed or Pieces?

When farmers grow potatoes from pieces, they produce exact clones of each variety. Seeds are not typically used because it's harder to predict or control what characteristics the offspring will have. But growing plants from seed is the only way to get a new potato variety. Plant breeders transfer pollen from the flower of one plant to the flower of another, then repeat this many times for years to produce a plant with the qualities that sui from that variety are used by growers to produce exact clones.

Eighty percent of the U.S. potato crop consists of only six varieties chosen for their resistance to certain pests and diseases and desirability for certain purposes (for instance, making great french fries!) With more than 5,000 known potato varieties, it seems a shame to depend on so few-remember what happened during the Irish potato famine when a whole nation depended on a single crop?

Many scientists developing new varieties recognize the importance of having access to wild native forms of potatoes with genes for different types of natural resistance and defenses. One threat to maintaining this "genetic diversity" is rapid deforestation which destroys many wild species of plants. Fortunately, there are people working to maintain seeds and tubers for a diversity of potato varieties.

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