Gardeners who grow potatoes face a lot of choices

Wisconsin might not be known for its potatoes, but the state is the nation's third-largest producer following Idaho and Washington. While this crop is typically grown on commercial farms, backyards can just as easily produce their own spud harvests.

There are many ways to successfully grow potatoes at home, Joey and Holly Baird explained in a Feb. 11, 2017 talk at the Wisconsin Garden Expo, recorded for Wisconsin Public Television's University Place. From backyard gardens to containers, potatoes are a versatile plant that can thrive in many conditions.

As founders of the The Wisconsin Vegetable Gardener, a multimedia educational program based outside Milwaukee, the Bairds know their potatoes, and the many distinctions between their various types. For example, sweet potatoes are related to the morning glory family and is a larger, sweeter root compared to plain old potatoes, which are nightshades and in the same family as eggplants and tomatoes. Altogether, there are about 5,000 varieties of potatoes thanks to genetic mutations and hybridization. Having originated in South America, they are now grown around the world.

Deciding what kind of potato to plant, however, depends on what end result a gardener is looking for.

"When you go purchase potatoes at your garden center or online, they have a description about the potato, and it does indicate good for canning, or good for cooking,” Holly Baird said. “If you're intentions are to can these, pressure can these, don't buy a potato that says not good for canning or doesn't mention that."

There are several myths about growing potatoes at home.

The first myth is that store-bought potatoes cannot be used for growing. Organic potatoes sold for cooking purposes can easily be used to for planting, though. Some store-bought potatoes are sprayed with a growth inhibitor that allows them to have a longer shelf life but prevents their use for growing, Joey Baird explained.

The second myth surrounds planting methods. It's commonly believed that planting two rows of potatoes together will allow the plants to grow more. This, however, is not the case, Holly Baird explained. In their experience, this approach has made no difference in yield.

When it comes to growing potatoes, one of the most important aspects of the process is fertilizer, Joey Baird said. Fertilizer can come in many forms, from dry grass clippings and leaf compost to used coffee grounds, which can be easily acquired from a local coffee shop. But he cautioned against using fresh (rather than "well-rotted") manure, since it has a high nitrogen level and will kill the plants.

Potatoes are also an excellent candidate for container gardening. Planting potatoes in containers requires several simple steps. A container should be filled about one-third of the way to its rim with potting soil and compost, at which point the potatoes should be planted. At that point, the plantings should be covered and the container filled up.

Joey Baird said it's important to make sure there are holes in the bottom of the containers being used because "potatoes can't swim and can't breathe underwater." The Bairds also recommend against using old tires for this purpose.

Key facts

• Three types of potatoes can be used for planting: early season, mid-season and late season. Each can grow from planting to harvest at about 75 to 90 days, 95 to 110 days and 120 to 135 days, respectively.

• The best place to plant potatoes is in a place with full sun, which means a spot that receives about six to 12 hours of sunlight a day. Another important consideration is soil temperature, which differs from air temperature. The minimum soil temperature for planting is 45 degrees. To measure soil temperature, a thermometer (such as a meat thermometer from the kitchen) should be inserted several inches into the soil. Anywhere between 45-50° F is optimal. The best air temperatures for potato plants to grow is when daytime levels reach 60-65° F and nighttime readings fall below 57° F.

• Potato tubers are the energy source from which a new plant will grow. Some growers prefer to trim the sprouts that grow from them, while others don't. While either method is fine, it's best to remove lone sprouts that aren't close to other growths. For example, if a potato has one sprout on its right side and two on the left, it would be best to remove the sprout on the right side and leave the ones on the left alone.

• There are several complications that can arise when gardening potatoes. Three common problems include: aphids, early blight and late blight.

• To chit or not to chit? Chitting potatoes is a means of speeding up the development of tubers. It's done by allowing sprouts to grow naturally out of direct sunlight, in a room temperature space, separate from each other. This growth can be achieved by placing potatoes in an egg carton or seed tray. Typically chitting is done six weeks before planting. While it isn't necessary, this approach can give plants a chance to jump-start their growth. Chitting may be advantageous for gardeners who live in areas with shorter growing seasons, such as northern Wisconsin.

• "No dig" potatoes can be a crafty way to grow without a garden. This process involves "planting" potatoes on the surface of an area and covering them with 18 to 20 inches of compost and watering regularly. When it's time to harvest, the compost is easily raked and the potatoes picked.

• When it comes to container gardening, it's important not to overcrowd a container. A 10-gallon container or grow back can support three to four seed potatoes, while a 15-gallon container can support five seed potatoes. Evenly spacing potatoes planted in containers is equally important.

This article was originally published on WisContext, which produced the article in a partnership between Wisconsin Public Radio, Wisconsin Public Television and Cooperative Extension.