Potato Magic: How to Grow Potatoes
Of all the root vegetables I grow, it is the potatoes that give me the biggest thrill at harvest time. I love to stick my hands in the soil and retrieve the buried bounty, with a yield of eight to ten potatoes for every one that I plant.
I Got Potatoes, They're Multiplying!
Potatoes are generous plants. Give them full sun, loose, fertile soil, and an inch of water per week, and believe me, they will accept almost any planting situation you offer them. You can grow potatoes in a plastic bucket, a plastic trash can, or special “grow bag.” But in my experience, containers like these require constant attention to watering, and yield only tiny harvests. A better plan is to grow your crop in a raised bed.
I achieve an enormous harvest—enough to feed my partner and me for nearly a year—by planting potatoes in two 4'-x-8' raised beds. The tubers are wildly prolific in the well-draining, rock-free soil the beds afford, and the vines require deep watering only once each week.
Kevin Lee Jacobs blogs at A Garden for the House. He was introduced to gardening when he was no taller than a delphinium. Today, his home in upstate New York features formal rose gardens outdoors and lavish window gardens indoors.
Choosing Seed Potatoes
However you decide to grow your potatoes, the planting directions are the same.
Start with organic, certified disease-free seed potatoes obtained from a catalog or farm store. (Supermarket potatoes that have been treated with a sprout-retardant are not suitable for planting.) If you buy from a farm store, as I do, try to select tubers which have already sprouted. Otherwise, pre-sprout them by simply laying them out on your kitchen counter. Pre-sprouted potatoes can be harvested a few weeks earlier than their non-sprouted kin.
Separate Your Eyes
Only small, golf ball–sized potatoes should be planted whole.
Cut large tubers into pieces. I cut mine so that each segment has two or three "eyes" (the little bumps from which sprouts emerge, as shown in the photo). The reason for cutting the potatoes is because the many eyes on a large potato will create a crowded, multi-stemmed plant, with each stem competing for food and moisture, and in the end, bearing only small potatoes.
Cures and Diseases
Next, "cure" the cut pieces. Either set them out in the sun, or place them on a table or counter in a warm (about 70°F), moderately lit room for three to five days. This step permits the cuts to become calloused. Calloused seed potatoes will help prevent rot.
And speaking of rot, let's talk about the dreaded "potato blight." This fungal disease—Phytophthora infestans—was responsible for the Irish potato famine and it can destroy your entire crop, too. To reduce the chance of infection, never plant potatoes (or tomatoes and other members of the nightshade family, such as eggplants or chili peppers) in the same patch of land without leaving an interval of at least three years. Also, promptly remove any volunteer potatoes that emerge in your garden. The disease overwinters in tubers left behind during the previous year’s harvest.
Plant Your Potatoes
In loose, fertile soil, plant each potato segment cut-side down in a 6-inch-deep hole or trench. Space each segment 12-inches apart on all sides.
Between each segment, sprinkle 2 tablespoons of a low-nitrogen, high-phosphorous fertilizer. Then cover both potatoes and fertilizer with 2-inches of soil, and water the soil well.
Keep Your Plants in the Dark
Because new potatoes form on lateral stems, or "stolons" above the seed potato, it’s necessary to "hill" the vines. When the green sprouts achieve 8 inches in height, bury all but their top 4 inches with soil, chopped straw, or shredded leaves. Hill again when vines grow another 8 inches. The more you hill, the more prolific your harvest is likely to be. I usually hill mine to a height of 18 inches. Stop hilling when the vines flower.
Potato tubers, like vampires, need to live in darkness. In fact, they will turn green if exposed to light. And a green potato can cause sickness if consumed. Therefore it is absolutely essential to keep the tubers covered with soil or mulch.
When and How to Harvest
Two weeks after the vines have flowered, you can, if you wish, reach into the soil or mulch and retrieve a few baby potatoes. Otherwise, wait until the vines die back. Dead vines signal that the tubers have reached maturity. Now reach into the soil with your hands and pull the tubers up.
Since my potatoes are grown for storage, I leave them in the ground until cool weather arrives. Why? Because potatoes will only store well if they are placed somewhere cold, but not freezing. The closet in my mudroom doesn’t cool off until the outside temperatures plunges to 45° at night. So harvest time for me is usually a sunny day in late October.
After digging the tubers, I let them sit on top of raised beds for a few hours to dry, as illustrated. This brief drying-period toughens their skin, and prepares them for storage. Then I gently brush off any loose soil from the tubers, and place them in double thicknesses of paper bags.