The potato ( Solanum tuberosum ) is a starchy tuber and one of the world’s most widely grown crops, making it a favorite for home gardeners. Cultivating this plant requires specific techniques to ensure a healthy yield of quality tubers. Successful potato growing involves careful preparation of the seed material, creating the proper soil environment, and consistent maintenance. This guide covers nurturing potato plants from the initial pre-planting stage through to harvesting and storage.
Selecting and Preparing Seed Potatoes
The selection of the initial planting material is the foundation of a successful potato harvest. It is strongly recommended to use certified seed potatoes rather than grocery store potatoes, as certified stock is guaranteed to be free from common diseases, particularly viruses, which can severely reduce yields. Grocery store potatoes may also have been treated with sprout inhibitors, further complicating their use for propagation.
Gardeners should choose varieties based on their desired harvest time, categorized as early-season, mid-season, or late-season (maincrop) types. Maincrop varieties generally require a longer growing period but produce larger yields and store better than the earlier types.
A process called “chitting” is used to encourage the formation of short, sturdy sprouts before planting. To chit, place tubers in a single layer in a bright, cool, and frost-free location, ideally between 7°C and 12°C. This encourages thick, green or purple sprouts; avoid warm or dark conditions, which cause long, brittle sprouts easily damaged during planting.
For larger seed potatoes, tubers can be cut into pieces roughly the size of a chicken egg, ensuring each piece contains at least one or two “eyes.” Allow these cut pieces to dry for one or two days until a protective, calloused layer forms. This drying prevents the cut surface from rotting in the soil and helps defend against pathogens.
Soil Preparation and Planting Techniques
Potatoes thrive in deeply cultivated, loose, and well-draining soil that allows tubers to expand without resistance. A dense or waterlogged environment can restrict tuber development and increase the risk of disease. Potatoes prefer a slightly acidic environment, ideally between 5.5 and 7.0, with a pH of 5.5 often cited as optimal for minimizing the incidence of common scab. The planting site requires full sunlight for optimal photosynthesis and robust vegetative growth.
Before planting, incorporate well-rotted compost or manure to improve soil structure and add essential organic matter. Since potatoes are relatively shallow-rooted, focus these soil improvements on the top 30 to 45 centimeters of the planting area.
A common planting technique involves digging a shallow trench, approximately 15 to 20 centimeters deep, or planting in individual hills. Place seed pieces in the trench with sprouts facing upward, spaced about 30 centimeters apart, and cover them with only a few centimeters of soil. This shallow initial covering is intentional, as it facilitates the subsequent, repeated process of mounding soil over the growing plants (hilling).
For gardeners with limited space or poor soil, potatoes can be successfully grown in large containers or specialized grow bags. This method requires a rich, loamy potting mix and excellent drainage to prevent the seed pieces from rotting. The initial planting depth ensures the seed potato is protected while allowing emerging shoots to quickly reach the surface and begin vegetative growth.
Ongoing Growth Care (Hilling, Watering, Feeding)
Once potato plants emerge, continued care focuses on hilling, consistent moisture, and nutrient management. Hilling is the practice of progressively pulling soil up around the growing stems, serving two primary functions. The first is preventing light from reaching developing tubers near the surface, which would cause them to turn green and produce the toxic alkaloid solanine. The second function is increasing yield by lengthening the underground stem, as potatoes form on specialized stems called stolons. Hilling should begin when plants are 15 to 20 centimeters tall, covering all but the top few leaves, and repeated every two to three weeks until flowering begins.
Potatoes have high water requirements, and consistent soil moisture is crucial during tuber initiation and bulking. Water stress during these stages can cause growth defects like hollow heart, knobby shapes, or cracking. Plants require up to 2 to 3 inches of water per week when tubers are rapidly expanding, often requiring irrigation to supplement rainfall. Watering deeply and less frequently encourages deeper root growth.
Reducing water application in the last few weeks before harvest helps the tuber skin thicken and “set,” improving storage potential. While nitrogen is important for early foliage development, excessive amounts later in the season promote leafy growth at the expense of tuber size. Potatoes are heavy feeders of potassium and phosphorus, especially during the tuber bulking stage. Apply a balanced fertilizer, often with a higher proportion of phosphorus and potassium (like a 5-10-10 ratio), at planting. Side-dressing with a potassium-rich fertilizer during hilling provides necessary elements for high-quality tuber formation.
Harvesting and Curing
Knowing when to harvest depends on the desired type of potato. New potatoes are smaller, thin-skinned tubers harvested early, usually about seven to eight weeks after planting, when the plant foliage is still green. For fully mature storage potatoes, wait until the foliage naturally yellows, withers, and completely dies back. Allowing the foliage to die back for two weeks ensures the tubers mature fully and their skin has hardened for better long-term storage.
When harvesting, use a digging fork instead of a spade to minimize piercing the tubers. Dig several inches away from the main stem and gently lift the entire hill to expose the potatoes. After carefully brushing off excess soil, the tubers must undergo curing before being placed in storage.
Curing is a wound-healing process that dramatically increases the storage life of the potato. This involves holding harvested tubers in a dark environment at a warm temperature, typically 10°C to 15.5°C, with high humidity (85% to 95%) for 10 to 14 days. During this time, the skin thickens, and any minor cuts are sealed with a corky layer known as the periderm. Store properly cured potatoes in a cool, dark, and slightly humid place, ideally around 4°C, to prevent sprouting and maintain quality.