How To Grow Potatoes
Plant Type: Annual
Scientific Name: Solanum tuberosa
Light: Full sun
Soil Type: Well draining, moderately organic
Soil Temperature: 50° +
ph Range: 4.8 – 6.0
Watering: Uniformly moist – especially during tuber formation
Plant (Payson): April 15 – July 1
Planting Method: Seed potatoes
Germination (days): 14 – 28
Transplant: Certified seed potatoes
Maturity (days): 90 – 110 days
Common Pests: Colorado potato beetle, flea beetles, aphids
Common Diseases: Blight – early and late
Potatoes prefer a sunny location in your garden, with loose, granular, sandy, deeply dug, fertile soil, that has good aeration and lots of good organic matter. A heavy clay soil will prevent the tubers from developing properly. Potatoes are heavy feeding plants if your soil is deficient add additional compost. A soil test can tell you which minerals and other amendments the soil may need. Potatoes prefer a slightly acid soil with a pH of 5.8-6.5.; however, they will usually produce a respectable crop, even if soil conditions are less than ideal. Do not plant potatoes where you have already grown either tomatoes, peppers, eggplants or potatoes in the past 2 years. Areas of the garden known to have grubs should also be avoided. Five pounds of seed potatoes will yield between 45 and 70 lbs. of potatoes and will require a garden area of about 10 x 12 feet—potatoes do not like to be crowded.
Potatoes are a cool weather plant and can be planted as soon as the ground can be worked in the early spring. Potato plants will not begin to grow until the soil temperature has reached 45-50 degrees F. The soil should be moist but not wet; if the soil is too wet the seed potatoes will probably rot before they even get started. If you want to store potatoes through the winter, you can plant a second crop as late as June 15—the plants will need some protection from the sun during the hottest months.
Because potatoes are susceptible to several diseases it is recommended that you use seed potatoes that are disease free and grown to provide the home gardener with maximum yields. Can you grow your own “saved” potatoes, yes, but even though they look healthy they should not be used. Certified seed potatoes are available at your local nurseries and garden centers at a nominal cost. There are over 80 different varieties to choose from—your local nursery will have varieties that are suited to our climate and that will do well in your garden.
A week or two before your planned planting date expose the seed potatoes to light in a warm area 60-70 degrees F, this will cause them to develop eyes/sprouts. A day or two before planting, use a clean, sharp knife to cut the potatoes into “seeds” that have at least 1 or 2 eyes/sprouts each. Small potatoes may be planted whole.
After a day or so, the pieces will form a thick callous over the cuts, which will help prevent it from rotting once planted. When planting your potatoes place the cut pieces so that the eyes are pointing toward the surface.
Potatoes can be planted in many different ways. They may be planted shallow in a trench 4 inches deep 8 to 12 inches apart. The benefit of shallow planting is that they will begin growing more quickly. When the seedlings reach 6 to 8 inches tall, pile a mound of loose soil/compost around the base of each plant to within 1 inch of the lowest leaves, this will prevent exposure to the sun and keep the potatoes closer to the surface for easier harvesting. Add extra soil/compost two to three weeks later.
Another method for planting potatoes uses holes wide enough to accommodate your seed potatoes at a depth of 7 to 8 inches. The potatoes will take longer to come up however this method eliminates having to add extra soil as the plants grow taller.
A method gaining popularity is growing potatoes under mulch or straw, in containers or in cages. The seed potato is placed in a shallow depression just deep enough to keep the top of the potato under the soil. Loose mulch is used to cover the potato to block sunlight. As potatoes shoots continue to grow additional mulch is added.
Potatoes can tolerate a light frost, but they should have some frost-protection when the plants are young. This can be a light covering of straw, compost, or tented with frost cloth. Pull weeds by hand, hoeing may damage the tubers. Watch for insect infestation, disease and grubs and treat appropriately. Remove diseased plants and put into the dumpster—do not compost.
Good water drainage and consistency is important when growing potatoes. If the soil is dense and clay-like you may want to add sand, straws, grass clippings, anything that will add organic matter to ensure proper drainage. Erratic watering stresses the plants and can cause dry holes in the tubers.
FERTILIZING Liquid organic fertilizer may be used at time of planting. Bone meal may also be beneficial to help maintain adequate phosphorous levels and encourage plant growth. Because potatoes are heavy feeders you may need to add nitrogen mid-way through the growing season. Word of advice: see your local nursery for organic fertilizer recommendations and soil testing.
WEEDING Should not be a problem if you carefully mulch as the potatoes grow. If weeds should appear pull them by hand to avoid damage to the growing potatoes.
DISEASE The best way to prevent disease and pests is to have healthy plants. Start with certified seed potatoes, use appropriate organic fertilizers, adequate consistent watering (moist not flooded) and eliminate weeds. Crop rotation will help to prevent soil-borne diseases. If treatment is needed, make sure that the measures are either organic or the pesticide used is organic and labeled for use on potatoes.
BUGS Aphids, flea beetles, blister beetles, leaf hoppers and potato grubs.
Early potatoes can be harvested when they reach an edible size. Gently feel around the soil and see how big they are—if they are too small do not leave the potatoes uncovered. Harvest potatoes when the vines have died and the potato skins have toughened up. Leave the potatoes in the ground for about 2 weeks after the vines die to make sure they are mature enough for harvesting. When it is time to harvest dig up them to gently to avoid damage, allow the tubers to dry for a day or two—do not remove dirt from the potatoes at this time—they will not cure properly. When ready to store gently remove dry soil by hand (do not wash your potatoes) and store in a dark location at 38° to 40° F.
If possible, store potatoes in a dark, humid place at around 40 degrees for maximum storage life. Keep potatoes in the dark to prevent them from turning green. Store only potatoes that are firm, not bruised, and free of cuts or breaks in the skin—one bad potato can ruin the rest. DO NOT wash them until you are ready to use them -moisture encourages decay. Don’t store potatoes next to onions or apples–they each exude a gas that shortens the life of the other. Potatoes can be dehydrated, frozen, or canned.