When Are Potatoes Ready to Harvest?

Many potato varieties exist, and plant-and-harvest cycles vary by region. With a little time and preparation, you could find yourself in a mountain of potatoes this fall.

by Jessica Walliser
PHOTO: JJ Hall/Flickr

Homegrown, freshly dug potatoes have a delicious flavor and buttery texture you probably won’t find in potatoes bought from the grocery store shelf. By following this simple guide to growing and digging potatoes, a huge harvest is easier than you might think.

Plant for a Good Potato Harvest

Potatoes are native to South America, where they were—and are—a staple crop for indigenous cultures. Once they arrived in Europe, plant breeders focused their efforts on creating the familiar edible tubers we’ve come to know and love today.

Select Potato Varieties

Hundreds of potato varieties exist, many of which boast distinct flavors, colors and textures. The first step in growing great potatoes is selecting the best variety for your climate and your tastes. Northern growers plant their potatoes in the spring for late-summer/fall harvests. In cooler climates, potatoes can be planted as early as two to three weeks before the average last-frost date in spring, but only if the soil has dried out a bit. Planting potatoes in wet soil can lead to rot. In the South, spuds are planted in late winter for a spring harvest, or in late-summer for a late-fall harvest. While most potato varieties do well in various climates, check with your cooperative extension or a few fellow gardeners to discover the best choices for your part of the country.

Prepare Seed Potatoes

Once you’ve selected a variety, purchase certified disease-free seed potatoes from a reputable source. These small tubers aren’t truly seeds but rather small, mature potatoes that are planted in the ground like seeds.

Before planting, cut seed potatoes into pieces. Each piece should contain at least one “eye” and be about the size of a half-dollar coin. These eyes are what sprout when you leave a potato in the cupboard too long. They’re easily found by searching the seed potato for small, dark indentations or, if the eye has already begun to sprout, swollen bumps.

After the seed potatoes have been cut into pieces, let them rest on the kitchen counter for a few hours to a few days before planting. This encourages a layer of callus tissue to form over the cut and helps prevent rot.

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Prepare Planting Sites

harvest potatoes
Susy Morris/Flickr

Select a potato planting site that receives full sun, and work plenty of compost into the area. Potatoes prefer a soil pH between 5.5 and 6.5, and soil that is well-drained. Waterlogged soils will cause the tubers to rot. Choose a spot, if possible, where other members of the nightshade family, such as tomatoes and peppers, have not been grown within the past few years.

Choose a Planting Method

Many methods of planting potatoes exist:

  1. Plant the tubers in rows, 6 inches deep and 12 inches apart.
  2. Dig a 10-inch-deep trench. Space the tubers at 12-inch intervals down its length, covering them only with a light layer of soil. Gradually fill in the trench as the plants grow.
  3. Plant three to five seed potatoes in a mound of soil.

Hill Your Potatoes

Regardless of which planting method you choose, hilling your potatoes is a necessary practice. Because the tubers are produced at the base of the plant just beneath the soil’s surface, hilling or mounding soil up around the base of the growing plants results in better potato yields and shields the developing tubers from light.

Hilling increases the underground surface area for tuber production, but an alternative to this process is to simply mulch your potato plants with a thick, 8- to 10-inch layer of straw. Not only does the straw layer serve to increase the underground surface area, but it also suppresses weeds and cuts down on the need for watering.

Wait for the Harvest

As your potato crop continues to grow, aside from regularly watering your spuds, there’s little to do until harvest time.

New versus Mature Potatoes

harvest potatoes
Susy Morris/Flickr

Potato harvesting can take place at two different times. If you’d like to harvest new potatoes—the young, immature potatoes whose skin has not yet hardened—for immediate consumption, the plants are ready for harvesting as soon as they start to produce flowers. Most gardeners sneak a few new potatoes from the edges of the growing plants by gently digging around with a gloved hand. You can easily harvest a handful of new potatoes while still leaving the plant intact for continued tuber production.

To harvest mature potatoes, look for a different set of clues. These tubers take a bit longer to develop, and there are a few necessary practices to ensure the spuds are truly ready for harvest and storage.

Signs Your Potatoes Are Ready To Harvest

Soon after your potato plants reach maturity, they come into flower. This signals that tuber formation has begun. The plants continue to grow for the next several months, and eventually the leaves and stems start to turn yellow and flop over. Mature storage potatoes are ready for harvesting a few weeks after the foliage has turned brown and died back completely. Tubers left in the ground have time to thicken their skins and properly cure before the harvest. This curing period is critical because harvesting potatoes early can cut down on their shelf life, whereas properly cured potatoes can be stored for many months.

Tips for Harvesting

harvest potatoes
Susy Morris/Flickr

Once digging time arrives, the real fun begins. A ritual akin to digging for gold, potato harvesting is easy.

  • Use the Right Tools: A digging fork or a three- or four-pronged potato hoe helps to gently pry up each plant.
  • Work Methodically: Start around the outside of the hill and work your way closer to the base of the plant. Get way down under the plant so you don’t spear any spuds.
  • Pick and Dig: As you pry and lift each plant out of the soil, the tubers are unearthed. Simply pick them up as they’re discovered, and use your hands to dig around in the loosened soil for any remaining potatoes.
  • Stay Dry: Harvest potatoes on a dry day if possible; it’s easier on you, the soil and the potatoes themselves.
  • Eat Damaged Potatoes Quickly: Damaged potatoes need to be consumed within a few days of harvesting.

Preparing Your Potatoes for Storage

harvest potatoes
Elizabeth Weller/Flickr

Once your potatoes have been harvested, brush off any excess soil with your hands. Be careful not to bruise or break each potato’s skin, and do not wash potatoes before storing.

The Curing Stage

Allow your dug potatoes to rest in a single layer for three or four days in a well-ventilated, dry location. Once they have rested, they’re ready for storage.

Root Cellar Storage

Potatoes are best stored in dark, cold conditions; between 45 and 55 degrees F is best. A dark, well-ventilated root cellar is a great place, but not everyone has one. If a root cellar isn’t an option, put your harvested potatoes in a wicker or plastic basket, a brown paper bag, or a cardboard box and store it in a dark basement or cool garage. Protect the tubers from light, and don’t layer them in the box or basket any more than a foot or so deep. Do not freeze them or store them in a refrigerator.

In-Ground Storage

Some gardeners prefer to leave their potatoes in the ground for storage and dig them only as needed. This is possible where the ground doesn’t freeze or become waterlogged with autumn rains. For this method, put a thick layer of fresh straw over the plants after they have died back, and dig the tubers up as needed. Some gardeners might experience a high rate of rot in potatoes stored in-ground, particularly during periods of wet weather. Also, potatoes stored in the ground are left vulnerable to voles, chipmunks, mice and other tuber-munching mammals that enjoy burrowing under the straw mulch.

Problems With Potatoes

harvest potatoes
Irene Kightley/Flickr

Potatoes can be a trouble-free crop if you follow a few simple practices, though they’re not immune to typical garden problems. Here are some you might face.

  • Insect Pests: To protect growing plants from foliage-munching Colorado potato beetles and flea beetles, cover the plants with a layer of floating row cover. These two pests can affect yields by reducing the amount of photosynthesis taking place in the leaves. It’s important to control them, if possible.
  • Garden Rodents: Voles and other rodents can be problematic to growers using straw mulch on their potatoes. If you find teeth marks on your harvested potatoes, you might need to set a few mousetraps inside sideways, empty tin cans to control them.
  • Potato Scab: Scars, scabs, lesions, craters and thickened spots on potato skins can be a sign of potato scab, a devastating disease that leaves potatoes looking less than desirable. Alkaline soils can encourage scab, so if this disease becomes a problem, aim for a new target pH of 5.0 to 5.2. To reduce your chances of a scab infection, plant only scab-resistant potato varieties, avoid using manure to amend your potato patch, don’t over-irrigate and rotate your crops.
  • Wireworms: If you notice small holes in your dug potatoes, wireworms might be the culprit. The soil-dwelling larvae of several different species of click beetles, wireworms tunnel into the tubers, creating shallow holes that extend into the potatoes only by about 1/2 inch. The holes are easily removed when the potatoes are peeled, but their presence can limit their storage life. Beneficial nematodes can be applied to the soil in the spring to help eliminate wireworms. Fall tillage also exposes wireworms to predators and freezing temperatures.
  • Sunlight Exposure: When potato tubers are exposed to sunlight, they produce chlorophyll and solanine, a glycoalkaloid poison. Green patches on the potatoes is evidence of sunlight exposure. Although solanine is found in many different members of the tomato family, green potatoes have enough to make you sick, so avoid eating any potatoes with green patches. To prevent greening, hill your potato plants.

Saving Small Potatoes For Spring Planting

harvest potatoes
The Art of Doing Stuff/Flickr

With a little extra effort, you can save your own seed potatoes for next year’s plantings. After harvesting, pull the smallest tubers from the bunch and store them in a dark box or bin, wrapped in layers of newspaper. Put the box or bin in a cold garage or root cellar, but do not let it freeze. The potatoes are shriveled by the time planting-time arrives next spring and they might have already sprouted, but the tubers can still be used.

The downside to saving your own seed potatoes is the increased risk of disease. Pathogens can easily overwinter on the seed potatoes and be reintroduced to the garden. Purchasing certified disease-free seed potatoes at the start of each season avoids this problem.

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