White potatoes, or Irish potatoes, are a popular root crop. They are grown from sections of potatoes or small potatoes saved from the previous growing season called seed potatoes, found in the spring at garden centres or farm and ranch supply stores. Potatoes found in grocery stores are treated with a sprout inhibitor, so they are not recommended for planting in the garden.
Choosing Seed Potatoes
There are many potato varieties, but only a few are found where seed potatoes are sold. The most popular white potatoes that have a brown or russet skin are Atlantic, lachipper and superior. Red-skinned varieties often available for planting in gardens are red pontiac and red lasoda. Always buy certified seed potatoes because they are inspected for disease. Seed potatoes should be firm and appear fresh. They will be dirty, because seed potatoes are not washed like potatoes found in the grocery store.
Processing the Seed Potatoes
Prepare the seed potatoes for planting at the right time, which is six weeks before the last average frost date. Seed potatoes are cut into pieces so more potato plants are produced. Each piece should have at least one eye. The eye is the indented area where a new sprout will form. Smaller seed potatoes that are the size of an egg or smaller can be planted whole. Spread the cut and whole seed potatoes over a flat surface in a well-ventilated area protected from freezing temperatures. Allow the cut seed potatoes to cure for two days, which means the cut area will become dried and shiny. Dispose of any potato sections or whole potatoes that are soft or mildewed after the curing period. Before planting, dust the seed potatoes with powdered agricultural sulphur to prevent fungal diseases.
Preparing the Planting Area
Clear an area of weeds and other vegetation so the bare soil is exposed and no weeds are present. Do not use any herbicides to clear vegetation because potatoes are very sensitive to herbicides. Dig a trench 2 to 3 inches deep for planting the potato sections. Each trench is a row and each row should be 3 feet apart.
Planting Potatoes and Expected Yield Per Plant
Place the seed potatoes with the cut side down in the trench. The potatoes should be 10 to 12 inches apart. Cover the newly planted seed potatoes with 1 to 2 inches of soil.
The average yield of potato plants is 4.54 to 6.8kg. per 10 foot row. If the seed potatoes are planted every 10 inches, the average yield would be 1 to 1.5lbs. per plant.
Care of Potato Plants
After the potato plants sprout, use a hoe to cover the vines with soil until only the top few leaves are exposed above the soil's surface. No more that 6 inches of the potato plant tops should be visible at one time during the growing process. Potatoes form along the growing stem of the potato plant, not the root mass. That is why you keep the stem covered; so more potatoes are produced. Covering the stem also keeps sunlight from reaching the developing potatoes. When potatoes are exposed to sunlight, they turn green and produce a toxic substance that tastes extremely bitter.
In late spring, the potato plants will produce a small purple flower, then the plants will quickly decline. When the plants begin to die, withhold water. Harvest the potatoes by pulling carefully pulling back the soil with a garden fork or hoe after the tops have completely declined. You can always pull a few small, or new, potatoes from the soil earlier in the season, without affecting the health of the potato plants.