Potato Gardening

Potato gardening requires a rich, loose, slightly acid soil. Use plenty of organic matter and add 5-10-10 or similar low-nitrogen fertilizer, about 10 pounds per 100 feet of row or as instructed on the fertilizer label.

The recommended soil pH for potato gardening is 4.8 to 5.4. If the soil is not acid enough, scab disease, which causes brown corky tissue on the potato surface, may be a problem. Lime soil for potatoes only if a soil test shows a pH below 4.8.

We get scab disease frequently here in Montana, where our soil pH is very alkaline. Good garden soil preparation involves adding organic matter which helps balance soil pH. Scab disease doesn't seem to bother anything, except the looks of the potato.

There are many other factors to consider when attempting to control this disease, however. To find out more about them (photos too), here is a link for you which will add to your potato gardening resources.

• Buy certified disease-free "seed" potatoes. This is important because potatoes can host many diseases that reduce growth but are otherwise undetectable in most gardens. It also makes good sense to avoid bringing potato disease to your garden.
• Good-size seed pieces increase the chances of a good yield. Cut them about 1-1/2" square, making sure that each has at least one good eye, and cut a week before planting to allow cut surfaces to heal slightly. Some growers dip cut pieces in dilute bleach solution or commercial fungicide to prevent rot. You can also plant small potatoes whole and avoid the risk of rot altogether.
• Set the pieces, cut side down, eye up, about 4" deep and 12" apart in rows 2-3 feet apart. (10-12 pounds of potatoes will plant 100 feet of row and yield 1-2 bushels at harvest).
• Potatoes form not on roots but on the stems rising from the seeds. Sprouts usually appear after 2-3 weeks - unless they were 1/4" or longer when planted or under less than 2" of soil.
• If spaced right, potato foliage will shade and cool the soil as the tubers mature, preventing damaging high temperatures. To further cool the soil, mulch 6" deep with a loose organic material.
• When plants are 5-6" high, hill up the mulch and soil around the growing stems. Potatoes exposed to light turn green, an effect associated with the naturally occurring poison, solanine. (Small amounts of green tissue can be scraped away, but excessively green potatoes should be discarded.)

To fertilize when planting, place seed pieces in the center of a 6" wide trench and work the fertilizer in at the edges with a cultivator. Do not let the fertilizer touch the seed pieces. Too much nitrogen fertilizer may cause excessive leaf growth at the expense of the tubers. Fertilize, but not too much.

Potato gardens need a steady moisture supply. If soil dries out after tubers begin to form, growth stops. It starts again as soil is watered. The result of this stop-and-start growth is misshapen, knobby, split, or hollow tubers. Try to keep soil moist to a 1 foot depth through the growing season. Barring rain, that normally means one heavy watering weekly.

• You can try growing plants from grocery store potatoes, but they frequently carry diseases and may have been treated to prevent sprouting.
• Do not over fertilize before tubers are formed.
• Do not ignore the best planting dates.
• Do not allow tubers to receive sunlight, making them green and inedible.
• Cultivate if necessary to reduce weed competition, but take care not to damage the shallow stems on which potatoes form.

Harvesting potatoes is fun and easy! It's kind of like unearthing treasure! You never know what you'll find; how many, how big...very exciting to the gardener who has labored so lovingly during the growing season.

Pick "new" potatoes as soon as the tops flower. New potatoes are not a variety, but simply any potato harvested before full maturity. They are smaller and more tender, but will not store. If soil is loose, simply reach in: otherwise, gently uproot the plant to check its progress.

Potatoes headed for winter storage need to mature fully in the soil. For full-size tubers, wait until the vines yellow or die back. Store them in the dark for a week or so at 70 degrees F to heal bruises and condition them. Then store them at between 35 and 40 degrees F, keeping humidity high.