The potato is a staple crop grown not from true botanical seeds, but from a specialized tuber called a seed potato. Proper spacing of these seed pieces is important for maximizing the final yield and promoting plant health. Adequate distance ensures each plant has enough light and nutrients, reducing stress. Strategic spacing also encourages sufficient air circulation around the foliage, minimizing the risk of fungal diseases.
Preparing Seed Potatoes for Planting
Before planting, gardeners often pre-sprout, or “chit,” seed potatoes by placing them in a cool, bright location for several weeks. This encourages the development of short, robust sprouts, giving the plant a faster start once placed in the soil. Larger seed potatoes, those bigger than a chicken egg, are often cut into smaller pieces to increase the number of plants. Each resulting seed piece should be 1.5 to 2 ounces and must contain at least one or two visible “eyes,” the buds from which the new plant will grow.
Once cut, the seed pieces must cure for two to three days in a warm, airy location away from direct sun. This curing process encourages the cut surfaces to form a protective, leathery layer called a callus. The calloused layer seals the interior starch, protecting the seed piece from rot and soil-borne pathogens. Planting calloused pieces ensures the best chance of successful germination, especially if the soil is cool and damp.
Standard Horizontal Spacing Guidelines
The physical distance between potato plants determines both the quantity and size of the harvested tubers. Two measurements guide the placement of seed pieces: in-row spacing and row-to-row spacing. In-row spacing is the distance between individual pieces within the planting trench, typically ranging from 10 to 15 inches apart.
Closer spacing (9 to 10 inches) forces competition, resulting in a greater number of smaller potatoes, often preferred as “new” potatoes. Spacing pieces farther apart (14 to 15 inches) gives each plant more room, yielding a higher proportion of larger, full-sized tubers. Row-to-row spacing, the distance between adjacent trenches, should be significantly wider, generally between 24 and 36 inches. This wider space accommodates mature foliage and allows room for hilling the soil.
Planting Depth and Hilling Maintenance
Potatoes are typically planted in a trench initially 4 to 6 inches deep. The seed piece is placed at the bottom and covered with a few inches of loose soil or compost. Tubers form above the original planting level on specialized underground stems called stolons. This upward growth habit necessitates the regular addition of soil around the stems.
This process is called hilling or earthing up, and it is performed as the plant grows to ensure the developing tubers remain covered. Hilling shields new potatoes from sunlight, which causes them to turn green and produce the toxic compound solanine. When the plant’s green shoots emerge and reach 6 to 8 inches, soil is gently mounded around the stems, leaving only the top leaves exposed. This practice is repeated several times throughout the early growing season, with the final mound reaching up to 10 or 12 inches high.
Adjusting Spacing Based on Potato Type
The maturity group of the potato variety is a factor in fine-tuning standard spacing recommendations. Potatoes are categorized into early-season and main crop varieties, which have different growth habits and harvest goals. Early or “new” potatoes, such as red or yellow varieties, mature quickly and are harvested while small. These compact types benefit from tighter in-row spacing, often planted 9 to 12 inches apart.
Main crop varieties are intended for long-term storage, require the longest growing season, and produce the largest tubers. These varieties, including many Russet types, need the widest spacing for full development and maximum size. For these slower-maturing types, in-row spacing should be increased to 14 to 18 inches. This distance allows the extensive root and tuber system ample space to expand without competition, resulting in a successful harvest of large, uniform potatoes.