Sweet potatoes (Ipomoea batatas) are a rewarding, heat-loving crop that can yield a substantial harvest even in limited spaces. Moving this vining plant into grow bags offers several practical benefits over traditional in-ground planting. Grow bags provide portability, allowing gardeners to maximize sun exposure throughout the day or move the plants to avoid unexpected cold snaps. This method also grants complete control over the soil composition, ensuring the tubers develop in the loose, nutrient-balanced environment they require. Furthermore, using containers simplifies the entire harvesting process, eliminating the effort of digging through dense garden soil.
Selecting the Grow Bag and Ideal Soil Medium
A single sweet potato plant requires a container with a minimum capacity of 10 to 15 gallons, though a 20-gallon bag can comfortably support two to three plants. Fabric grow bags are the superior choice because the porous material allows for “air-pruning.” This encourages dense, fibrous root growth instead of long, circling taproots, signaling the plant to focus energy on developing edible tubers.
Sweet potatoes require a location that receives full, direct sunlight for at least six to eight hours each day. The soil medium inside the bag must be loose and well-draining to allow for the expansion of the developing roots. Avoid using heavy native garden soil, which compacts easily and can lead to misshapen or stunted tubers.
The ideal substrate is a blend that promotes aeration and retains moisture without becoming waterlogged. A mixture incorporating one-third compost, one-third peat moss or coir, and one-third perlite or vermiculite creates the necessary structure. Avoid fertilizers high in nitrogen, as excessive nitrogen encourages abundant leafy top growth at the expense of tuber development.
Planting Sweet Potato Slips
Sweet potatoes are propagated from “slips,” which are vine cuttings or sprouts taken from a mature tuber. Planting should be delayed until the danger of the last spring frost has passed, and the soil temperature consistently registers above 60°F. Many growers wait until the soil reaches 70°F to 75°F to ensure rapid establishment, as sweet potatoes are highly sensitive to cold soil.
Upon receiving the slips, hydrate them immediately by placing the cut ends in water for a few hours. Each slip should be buried deep into the soil, leaving only the top two or three leaves exposed above the surface. Planting deeply is beneficial because the entire length of the buried stem is capable of developing new roots and forming tubers.
After positioning the slips—about 12 inches apart in a larger bag—the soil must be thoroughly soaked. This initial deep watering settles the medium around the newly planted roots, eliminating air pockets and establishing good soil-to-root contact.
Ongoing Care and Maintenance
Grow bags facilitate excellent drainage and aeration, meaning they dry out faster than in-ground garden beds. Consistent, deep watering is necessary, especially during periods of high heat, to prevent the soil from drying out completely. Keep the soil evenly moist, not saturated, to support continuous tuber enlargement.
Sweet potatoes are not heavy feeders and perform best when fertilized lightly with a low-nitrogen formula. Applying a fertilizer with a higher ratio of phosphorus and potassium every four to six weeks encourages the production of storage roots rather than just foliage. Excess nitrogen results in lush green vines but a disappointing harvest of small tubers.
The long vines, or runners, will eventually drape over the edges of the grow bag and attempt to root into the surrounding ground. This rooting process is undesirable because it redirects the plant’s energy away from the main tubers inside the container. To prevent this, regularly lift and turn the runners, a process known as “pinning,” to break any small roots that have begun to form outside the container. For vining varieties, trimming the ends of the runners that extend far from the bag can also help manage the plant’s resources.
Harvesting and Curing
Sweet potatoes reach maturity between 90 and 120 days after planting the slips. The best indicator that the tubers are ready for harvest is when the plant’s leaves begin to yellow and die back naturally. Harvest the crop immediately before the first expected frost, as cold temperatures damage the roots and negatively impact their storage potential.
The grow bag method simplifies harvest, reducing the risk of accidentally slicing or bruising the roots. The gardener can simply tip the bag onto a tarp and gently sift through the loose soil to collect the tubers. Handle the sweet potatoes with care to avoid cuts and scrapes, which can introduce pathogens and shorten the storage life.
After harvesting, sweet potatoes must undergo a two-step conditioning process known as curing. Curing converts starches into sugars and heals minor skin damage. The initial step requires placing the tubers in an environment maintained at 80°F to 90°F, with high humidity (around 85 to 90 percent), for four to seven days. This warm, humid period allows the skin to thicken and small wounds to seal.
Following the initial curing phase, the sweet potatoes are ready for long-term storage in a cooler environment. The ideal storage temperature is between 55°F and 60°F. Temperatures below 54°F can cause chilling injury, leading to internal discoloration and a hard center when cooked. Properly cured and stored sweet potatoes maintain their quality for several months.