How to Grow Potatoes
How to Plant Potatoes for an Abundant Harvest
By Nancy Pierson Farris – What can be red, white, or blue, provides healthy carbohydrates, and grows underground? In my area, it’s known as the “Irish potato.” In the 17th century, the potato became the main food source in Ireland. In the 19th century, the potato crop was destroyed by blight, creating a famine during which thousands starved to death in Ireland, and many emigrated to America. In 21st century America, people consume potatoes as fries, chips, or instant mashed. Those who have never tasted a freshly dug potato haven’t experienced true potato flavor. This article is a tutorial for how to grow potatoes and enjoy their delicious taste and versatility.
The potato depends on long days and warm temperatures to make a good crop. However, the plants don’t thrive on intense summer heat. In my location, at the upper edge of coastal South Carolina, summer days average five degrees hotter than locations along the coast. On those hot, humid days, potato plants wilt and turn yellow. I must plant potatoes early so they can mature before the brutal heat arrives.
We begin well before planting time by digging a fairly deep trench into which we spread compost. Experts recommend doing this as early as the previous fall, to allow the compost adequate time to rot. Fresh manure may exacerbate problems with scab on potatoes.
For many years, when learning how to grow potatoes, we failed to realize the importance of pH. According to USDA, potatoes prefer 5.0 to 5.5 pH. Too much wood ash or lime can make the soil too alkaline and crop yields will be reduced. Too much pine or oak mulch raises the pH and the potatoes will be small and poor in quality. In our area, which is undergirded by limestone, the pH of the soil can be lowered simply by irrigating with the groundwater from our well. We use mulch that acidifies the soil: pine straw and oak leaf mulch are readily available to us.
Wondering when to plant potatoes? We start planting potatoes about a month before our last frost. If we do get a light frost after the potatoes start to come through the ground, we leave the blackened tips, because the plants will almost always send up more sprouts.
Traditionally, small potatoes left from the previous year were used as potato seed or more commonly known as seed potatoes. They usually have sprouts by early spring. I still do this, although experts advise against it, citing the possibility of disease organisms in the old potatoes. I also buy seed potatoes every spring—about three pounds for a 50-foot row. Red or white normally refers to skin color, though Mountain Rose produces red flesh.
I cut the seed potatoes into pieces about the size of a hen’s egg, taking care not to break off any sprouts, and I make sure I have at least two or three “eyes” on each piece. After cutting, I spread the pieces in a single layer on a tray or a shallow cardboard box, and set them on my screened porch in a lighted spot, but not in direct sunlight. I let them dry for a couple of days. Some people dust the pieces with fungicide before planting.
For those who haven’t prepared a furrow with compost, USDA recommends about 3/4 pound of 5-10-5 fertilizer for a 50-foot row. Simply make a six-inch deep furrow and sprinkle in the fertilizer. I would cover that with about an inch of soil, then lay down the seed potatoes.
We loosen soil in our prepared furrow and place the pieces of potato about 12–15 inches apart and cover with about three inches of soil. After the potatoes have sprouted and shown good growth, we hill more soil up around them to ensure that tubers will not push up through to the surface; sunlight will turn them green and may cause bitterness.
About six or eight weeks after plants start to grow, tubers begin to form underground. The USDA says, “contrary to much common opinion, development of tubers does not depend on flowering.” I would not argue with the experts, but in my experience, flowers usually signal that tubers are forming. This is exciting, because from that point, I know I can “grabble” a few tender new potatoes for lunch. Cooked with early green peas and seasoned with a bit of butter and cream, this makes a meal that is a suitable reward for a hard-working gardener. When I harvest these little potatoes, I take care digging around each plant, so as not to break off smaller tubers—and I only remove one little potato from each plant, leaving plenty to mature for our main crop.
During the growing season, potatoes need little attention unless insect pests invade. If leaves start to curl and growth seems to slow, look for aphids. They are small, flat, soft discs with legs. The peach aphid is green and overwinters on peach trees. In Northern climates, buckthorn aphids overwinter on buckthorn and may attack potatoes. That aphid may be yellow, green, or black. The pink and green potato aphid overwinters on roses. A strong spray from a garden hose will usually dislodge aphids. In my garden, ladybugs arrive in time to clean up aphids from early spring crops.
The worst pest for me has been the Colorado potato bug. Fact is, the voracious insect is yellow with black decor, nearly a half-inch long and it attacks potato plantings anywhere in the United States. I watch my plantings carefully because if the beetles come, I must take swift action to prevent losing the crop. There are chemical sprays, but I don’t like to put toxic materials into my garden and chance hurting bees and birds.
A thick mulch may prevent beetles from attacking. At the Rodale Experimental Farms, a one-foot layer of straw mulch under the plants prevented the beetles from climbing out of the ground and up the stems of potato plants.
When is it time to harvest? We want those potatoes to get as large as possible, but we don’t want them damaged by underground critters. According to Clemson experts, fire ants do not eat vegetables. However, we have seen fire ants on potatoes—perhaps they are seeking moisture? Whatever their purpose, they damage the crop. We check regularly and if we find potatoes with tiny holes, or potatoes with bite marks that indicate mice or voles are coming to dinner, we claim our underground crop immediately. Some years, we harvest because the plants are wilting and turning yellow. That may happen because of too much or too little rain, or because of insect attacks. In any case, if the plants start to deteriorate, we harvest the potatoes.
I have never grown All Blue potatoes, which have blue flesh. Maybe I will try a few plants next spring. Combining All Blue with Mountain Rose would make a really impressive potato salad for Independence Day! I hope this article is helpful in learning how to grow potatoes.
Published in Countryside November / December 2014 and regularly vetted for accuracy.