Growing Potatoes
IF YOU MUST DELAY PLANTING: If you need to store your potato minitubers before planting them, keep the bag in a cool (40-50°F), well-lit place. The eyes may begin to form chubby little sprouts, but this just indicates that they are ready to grow. Do not remove these sprouts. If the potatoes are stored in a warm, dark place, however, they will make long pale shoots, which will weaken the plants.
PLANTING AND CARING FOR YOUR POTATO CROP
1. In spring, when the soil has dried enough to be workable (about 2-3 weeks before the local frost-free date), prepare a deeply worked bed in a sunny spot that is as free of weeds and soil clumps as possible. Potatoes prefer soil with a pH of about 6. Don't plant potatoes where you grew potatoes, tomatoes, peppers, or eggplant the previous year. If the ground is fertile, no additional fertilizer is necessary. Too much nitrogen will cause lush top growth at the expense of tubers. Do not use fresh manure as it can cause potato scab (see "Next Year's Crop" below); finished compost or aged manure is fine. Work the compost or aged manure into the ground well ahead of planting, or top dress afterwards. A cover crop plowed under before the season begins is an ideal way to increase fertility.
2. Dig a shallow trench 3-4in deep and 3in wide at the bottom. The edge of a hoe is good for this job. Rows should be 24-36in apart.
3. Plant the minitubers about 12in apart in the row. (If the tubers are big, it's fine to cut them in half. Just be sure each piece has 2 or 3 eyes, and dip the cut face of each half in agricultural lime after you've cut them.) After planting, use a rake to cover the minitubers with 1-2in of soil.
4. When plants are 6-8in tall, fill in the rest of the trench from both sides by gently pulling the soil up with a rake or hoe, leaving about 4in of the leafy plant exposed. Be careful not to damage the roots.
5. Continue to hill up soil or mulch heavily as plants grow. This increases yields by providing more room beneath the soil surface for potatoes to form.
6. Watch for insects, and use appropriate controls if they become a problem. Bt (Bacillus thuringiensis) can be helpful in dealing with potato beetle larvae. Pyola® Insect Spray or Neem products are effective in controling adult potato beetles.
7. Potatoes require at least 1in of rainfall per week while actively growing. Water your plants thoroughly if there is no rainfall. To determine whether they need water, check the plants in the morning when it is still cool. If the growing tips are wilting, water deeply.
HARVESTING NEW POTATOES: After 60 days or so, plants will flower and little tubers will begin to form on underground stems called stolons. Some varieties either bloom very late or not at all, so check for new potatoes after 65-75 days on plants that don't bloom. Gently probe around the base of the plant for developing tubers on the ends of stolons (some stolons are as long as 18in). Dig up only enough baby-sized potatoes for one or two days' use, as they are perishable. While it's a treat to harvest some of your crop as new potatoes, leave most of the crop to mature for later harvest and storage.
HARVESTING YOUR MAIN CROP: For your main potato crop, allow growth until vines naturally wither or until tubers have reached the desired size. Frost will encourage maturing. If tubers are fully formed and continue to produce vigorous top growth, break the tops off at ground level to stop growth. Allow the tubers to remain in the soil at least two weeks after tops have died back or have been broken off. Don't water plants during this period. This provides time for skins to "set," which increases storage life. Dig potatoes carefully with a fork so as not to bruise or damage skins. Dig deeply and at a distance of up to 18in from the plant to locate all tubers. Injured tubers should be cooked and enjoyed right away. Potatoes will turn green and taste bitter if stored in the presence of light. For this reason, we recommend storing them in brown paper bags at low temperatures; 35-40 degrees F is optimal. Cool temperatures retard sprout development and increase storage life. Do not store potatoes in the refrigerator; the atmosphere is too dry for them to keep well.
NEXT YEAR'S CROP: Scab is a common disease in potatoes. It makes them unattractive and reduces storage life. Planting clean seed, such as ours, in loose, well-drained soil reduces the risk of scab. Moist soil is required during the development of tubers, but the soil should not be soggy. Growing potatoes in soil with a pH above 6.5 can increase scab problems. Take care to harvest your entire potato crop; don't leave any tubers in the soil. Weed out any volunteers as they emerge to eliminate potential sources of scab and virus for future potato crops -- do not leave volunteer sprouting potatoes in the ground. Also, rotate the location of your potato bed so you do not grow potatoes in the same spot again until at least 4 years later.
