Growing potatoes in containers has become a popular method, especially for gardeners with limited outdoor space. A grow bag is a fabric container designed to provide breathability and superior drainage, offering an efficient alternative to traditional in-ground gardening. The size of this container is a significant factor, directly influencing the eventual yield and the health of your potato plants. Choosing the right volume ensures the plant has the necessary space to develop its tubers and allows for essential growing techniques.
Why Container Size is Critical for Potato Yield
The volume of the grow bag is not simply about accommodating the root system, but rather about allowing for the unique growth habit of the potato plant. Potatoes form new tubers not from the original seed potato, but from underground stems called stolons. These stolons produce tubers above the initial planting level, along the buried portion of the stem. This requires the technique known as “hilling,” where soil is repeatedly added around the emerging stems. Grow bags must provide sufficient depth and volume to support this continuous hilling process. If the container is too shallow or narrow, it limits the space for hilling, severely restricting the number of tubers that can form. A container with insufficient volume will reduce the overall harvest.
Specific Size Recommendations Based on Potato Variety
The correct grow bag size depends on the specific potato variety you choose, which are broadly categorized as either determinate or indeterminate.
Determinate Varieties
Determinate varieties, often early-season potatoes, produce their tubers in a single layer relatively close to the seed potato. These varieties do not strictly require repeated hilling to be successful, as the tubers will set in the bottom section of the bag. A minimum size of 5 to 7 gallons is sufficient to support two to three seed potatoes, allowing for a good yield of smaller, “new” potatoes.
Indeterminate Varieties
Indeterminate varieties, typically maincrop or late-season types, benefit most from the grow bag’s vertical space. These potatoes form tubers along the stem as it grows upward, requiring continuous hilling for maximum production. A 10-gallon to 15-gallon grow bag is suitable for three to four seed potatoes. Choosing a 15-gallon or 20-gallon bag provides the best potential for a high yield of larger, storage-friendly potatoes, as it offers the greatest vertical capacity for hilling. Fabric grow bags are preferred over plastic containers because their breathable material allows for superior drainage and air pruning of the roots.
Preparing and Planting Your Potato Grow Bag
Preparing the planting medium is essential to ensure a successful crop. Potatoes perform best in a loose, well-draining soil mix that allows the developing tubers to expand easily without resistance. A quality potting mix blended with compost provides necessary nutrients while maintaining good aeration. Avoid using heavy garden soil alone, as it compacts easily in a container, restricting tuber growth and impairing drainage.
To begin planting, roll the grow bag down to about half its height to facilitate initial hilling. Place a base layer of four to six inches of the prepared soil mix in the bottom. Lay the seed potatoes (which should be “chitted” or pre-sprouted) on this base layer with the sprouts facing upward. For a 10-gallon bag, plant two to three seed potatoes, spaced evenly. Cover the seed potatoes with three to four inches of the soil mix, and thoroughly water the bag to settle the medium.
Ongoing Care and Harvesting
Ongoing care is necessary for maximizing the yield, particularly concerning moisture and nutrient levels. Fabric grow bags can dry out faster than in-ground garden beds due to the increased surface area for evaporation. Consistent watering is important to maintain even moisture, but the soil should never be allowed to become soggy, which could lead to tuber rot.
Potatoes require a consistent supply of nutrients throughout their growing cycle. Applying a balanced fertilizer, or one higher in potassium, is beneficial once the plants are established to encourage strong tuber development. The hilling process should be continued as the plant stems emerge; add more soil mix until only the top few leaves are exposed, gradually unrolling the bag until it is full. Harvesting is signaled by the plant’s foliage beginning to yellow and die back, indicating the tubers have reached maturity. For maincrop varieties, waiting two weeks after the foliage has died completely allows the potato skins to set, improving their storage life before the bag is emptied for harvest.