What is the best way to grow potatoes in containers?

A Question of the Week
potatoes

Growing potatoes in containers is a great option for anyone who has limited space to garden, is concerned about what is in their soil or is looking for an easier way to harvest potatoes. Almost any vegetable can be grown successfully in a container, and potatoes are no exception.

Though you may not harvest as many potatoes in a container as from garden soil, given the right growing conditions, a single potted potato can produce a considerable number of tubers. All it takes is growing them in a location that receives at least 6-8 hours of direct sunlight a day, choosing the right container and providing enough water.

Choosing and Preparing Seed Potatoes

Potatoes in containers usually don’t get quite as big as their soil-grown counterparts. Rather than trying to grow large russet varieties, container gardeners will likely have better luck growing small “new” potatoes. Potato varieties are also distinguished from one another by how soon they are ready for harvest.

In general, mid or late-season varieties are better choices for containers than early-season types because they will continue to form tubers over a longer period of time. “Seed potatoes,” which aren’t seeds but small potatoes used to grow new plants, should be purchased from reputable seed catalogues or garden centers in the spring. Don’t bother trying to plant grocery store potatoes because these are often treated with chemical sprout inhibitors that will prevent new growth.

Twenty-four to forty-eight hours before planting, seed potatoes need to be prepared. Large seed potatoes can be divided into pieces to produce multiple different plants. As long as a seed potato piece has one or more “eyes,” it should grow into a new potato plant.

Potato eyes are small dimpled areas that contain vegetative buds. Large seed potatoes should be cut into 1-2” diameter pieces that have at least one eye, while small seed potatoes can be planted whole. Allow cut pieces to air dry for a day or two in order to reduce the chance of rotting.

Picking a Container and Potting Soil

A wide variety of different containers can be used to grow potatoes. While it is possible to purchase ready-made potato towers or special growing bags, any opaque container with drainage holes will do, including barrels, garbage bins, plastic storage tubs and chimney flues.

An ideal container will be about 2-3 feet tall with a 10-15 gallon capacity. Avoid containers that are taller than this, because it could be difficult to water them evenly; the top portion of tall containers usually dries out long before the bottom, which can remain soggy and cause potatoes to rot.

Using the right potting mix is just as important as picking a good container. In the ground, potatoes grow best in fertile, acidic, well-drained soils. However, the same garden soils that are good for potatoes grown in the ground can be a poor choice for containerized plants.

Garden soil compacts easily, dries out quickly, yet drains poorly and can contain weed seeds and diseases. Instead, fill containers with a half-and-half mixture of “soilless” potting mix and quality compost. Peat-based potting mixes are lightweight, retain moisture and readily shed excess water, and compost adds important nutrients. Both pre-made soilless potting mixes and bagged compost are available at garden centers.

Planting

When it comes to planting seed potatoes, it is important to understand how potato plants develop. After a seed potato has been planted, it grows a main shoot. Rhizomes, which are underground stems, develop off the main stem and produce tubers at their tips.

This means that potatoes are formed above where the original seed potato was planted. When additional soil is mounded around the main stem of the potato plant, new rhizomes will form below the soil line and more tubers will develop.

When getting ready to plant, start by filling the container with about 6-8 inches of potting soil. Next, place seed potatoes within the container, spacing them about one foot apart. The number of seed potatoes to plant depends on the size of the container.

To maximize health and productivity, plan for five gallons of soil volume for each plant. After placing the seed potatoes, cover them with an additional six inches of potting soil. As the growing season goes along, continue to add more soil to the container, leaving six or so inches of foliage exposed at any given time.

Watering and Fertilizing

Adequate watering and fertilization is essential for heathy plant development. The potting soil in containers should be kept moist but never soggy. Water whenever the top 1-2 inches of soil feels dry to the touch, and apply enough water for some to escape out of the bottom drainage holes.

Potatoes require lots of nutrients throughout the growing season to produce new growth and quality tubers. Once shoots emerge, begin using a balanced soluble fertilizer once every couple of weeks.

Choose a product that has a higher middle number (phosphorus) than the first number (nitrogen), because while potatoes need nitrogen to grow heathy green leaves, having more phosphorus is important for tuber production. Synthetic fertilizers with a nutrient ratio of 5-10-10 are good choices. Organic growers can instead use a combination of fish emulsion, greensand, kelp meal and bone meal to feed their plants.

Harvesting

Mature potatoes can be harvested once the tops have yellowed and started to die back, or after the first frost in the fall. Often the easiest way to harvest container-grown potatoes is to spread out a tarp and tip the container onto it. Sifting through the soil should quickly reveal an abundance of tubers.

Handle the potatoes gently – they can bruise – and move them to dry in an area out of the light to avoid greening. Brush excess dry soil from potatoes but don’t wash them until you’re ready to use them. Washing can injure the skin and promote rot. Finally, store the potatoes in a cool, moist, dark environment such as root cellar or basement.


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