Potatoes: Earth Apples (as the French say)

By Jane Shellenberger:

When I traveled to Peru years ago to visit my daughter, we took the bus from Arequipa, in the south, to Cabanaconde, the end of the line at the top of the Colca Canyon, where the condors live. Late in the day, a few miles out from town, the bus stopped in a couple of spots to pick up sunbaked Peruvians, mostly woman, with thick, shiny blue-black hair who stashed huge sacks of potatoes and their shovels in the luggage compartment below then climbed onboard, usually with a baby or two tucked into their bright clothing. If they were lucky, the bus wasn’t filled with tourists and they found a seat; otherwise they stood.

In the little groceries we saw the the huge sacks, each one open at the top to display snowy white, pink, purple, red, brown, or golden yellow potatoes, round or oblong, from peanut-sized to small- and medium-sized. I’ve read that one Peruvian valley might have over a hundred different cultivars.

A few days later, as we headed back to the city early in the morning, the bus stopped to let off several Peruvian women, each with a shovel and an empty sack or two. As the bus roared off, we watched them climb the steep hillside for a day of digging and tried to envision them dragging such heavy sacks of potatoes down the hillside to the road.

In 1536, as the Spanish battled and eventually conquered the Inca in Peru, they brought the potato back to Europe. Since Peru is close to the equator, the potato was adapted to a different day length and climate, and it didn’t yield much. Eventually it was bred to become a better crop, but since breeding had begun with just a few varieties, the potato was not genetically diverse and was vulnerable to disease. In 1845, late blight destroyed the entire crop in Ireland, causing the Irish potato famine.

Today there are many varieties of potatoes available to plant in home gardens—at least sixty—and they are much more delicious with a much higher protein content than the big starchy russets that some of us grew up eating as fries and bakers. Many are loaded with high-potency antioxidants called anthocyanidins, which have been shown to strengthen the immune system and reduce age-related memory loss and the risk of some major diseases.

Potatoes like our high altitude with intense UV sunlight, much like their native Peru. They grow best in sandy, well-drained soil with a lot of organic matter and minerals, but not too much potassium, which produces higher starch and lower protein content. Most Front Range soil is clay and already contains a good amount of potassium, but if you build your soil and microbe population by adding compost and other organic amendments over time, it will balance itself out so don’t worry about it.

Always buy “certified seed potatoes.” There is no such thing as a “certified disease-free” seed potato, according to Paul New of White Mountain Farm in Mosca, Colorado, who grows a lot of organic potatoes. Because they are susceptible to dozens of diseases, and because they are grown in a concentrated way, no one can guarantee disease-free potatoes. To prevent blight, New sprays the leaves with a concoction of compost tea, kelp, and fish emulsion.

Where rotting is an issue, it’s recommended to chit seed potatoes by laying them out in a brightly lit room, but not in direct sun, for several weeks so the sprouts are already growing before planting. This is much less of an issue in our climate, but do it if you want. Seed potatoes don’t look any different than regular potatoes.  When you cut the larger ones up for planting, make sure each piece has at least two eyes or sprouts and is at least as big as a golf ball.  Handle them carefully as the sprouts can break off. Let the cuts callous over to cure for a few days before planting.

To avoid disease, plant potatoes where other nightshades (tomatoes, tomatillos, peppers, eggplants) or raspberries haven’t being growing for a few years. Depending on the weather, plant on the plains around March 15 to May 1 (I’ve had some success planting even later too, but the harvested potatoes are smaller), mid-May to early June in the mountains. The leaves can be nipped by a hard frost, which will set back growth but usually won’t kill them. If you’re preparing a new bed in the spring, do it when soil isn’t wet. Loosen the soil deeply with a fork so compost can sift down to the lower soil levels; this helps potato roots. Mix straw into the soil to keep it loose.

The traditional way to grow potatoes is to hill them. After planting the pieces 4 inches deep with sprouts facing up in a trench that’s about 12 inches wide or in the middle of a three- to four-foot-wide raised bed, cover them up carefully. Space them about 12-18 inches apart, or more if dry conditions are a concern. As the stem and leaves grow at least 4 inches aboveground, mound up soil, or straw and soil, covering a quarter of the new growth. Keep mounding up soil and straw over another quarter of the new growth every week or two. This mound is where the potatoes will grow. Water consistently.

For those with less time and, like me, less inclination to follow through on the hilling, you can try the easy sheet–mulcher’s method. Plant potatoes several inches deep and cover them with a thick layer of straw or hay mulch (you want 6–8 inches minimum after it has settled). Hay comes in flakes, which you can partially pull apart, but don’t spend a lot of time pulling them completely apart; partial flakes are fine because you want a thick layer. The plants are strong enough to push right up through the mulch, often causing a hay cone to erupt before they break through. The thick mulch also helps to hold up the young plants and protect them from wind. When the plants grow taller, add more mulch. The potatoes will grow in the dark layers. The key to mulching with hay in a vegetable garden is to lay it on thick. If green hay grass starts growing, your mulch isn’t thick enough. Famed sheet mulcher Ruth Stout didn’t even “plant” potatoes—she just threw the pieces on the ground and covered them up with thick hay.

As the flowers form aboveground on the plant, the underground tubers begin to form too, and it’s especially important to keep the plants watered at this stage. Water less later, after the potatoes have formed.

Harvest with a fork to prevent cutting into the potatoes. Potatoes mature in 65–120 days, depending on the variety. They turn green and semipoisonous if they grow in sunlight near the soil’s surface, so discard these or cut out the green part. Store long term at about 40 degrees after curing for a few days at 50–60 degrees; they will also store well for months if left in the ground.