The sweet potato (Ipomoea batatas) is a vining root crop belonging to the morning glory family. Unlike the common potato, the edible portion is a storage root, not a true tuber. This tropical plant is grown from a shoot or cutting called a “slip,” not from seeds or a whole potato placed directly into the ground. Starting with a sweet potato that has already begun to sprout offers a head start on generating these slips. This process transforms a single sprouting root into multiple viable plants, each capable of producing a full harvest.
Generating and Curing Slips
The first step is to generate and prepare the planting material from the sprouting root. While the traditional water method works, partially burying the potato in moist potting mix or sand is often more effective for encouraging vigorous shoots. This method provides the necessary warmth and moisture, typically generating slips within three to six weeks. Slips are ready for separation when they reach six to twelve inches long, complete with several leaves.
To separate a slip, gently twist or pull the shoot away from the mother potato at its base. This process can be repeated as new slips develop, allowing a single sweet potato to yield numerous plants. After removal, the slips must undergo a brief curing period. The freshly cut end should dry for one to two days in the air to form a protective layer, which helps prevent rot and disease. Following this, place the slips in water for about a week to encourage root development before transplanting.
Soil and Site Requirements
Before transplanting, the outdoor environment must meet the specific requirements of this heat-loving plant. Sweet potatoes are sensitive to cold, so planting should occur only after the danger of frost has passed. Nighttime temperatures must consistently remain above 55°F (13°C). The soil temperature is equally important, needing to be consistently warmed to at least 60°F (15°C) to 65°F (18°C) at planting depth for successful establishment.
The planting site must receive full, direct sunlight for a minimum of eight to ten hours daily to support tuber formation. A loose, well-draining, sandy loam is recommended, as dense or compacted soil can result in misshapen and smaller roots. The soil should be slightly acidic, aiming for a pH range between 5.5 and 6.5.
Sweet potatoes require a relatively low level of nitrogen compared to other crops. Excessive nitrogen promotes the growth of lush, sprawling vines at the expense of developing storage roots. Focus on soil amendments that enhance drainage and provide moderate phosphorus and potassium levels to support better tuber production.
Step-by-Step Planting Technique
To maximize the harvest, plant the prepared slips using a technique that encourages root initiation along the buried stem. Creating raised rows or mounds eight to ten inches high is beneficial, as this aids drainage, allows the soil to warm faster, and provides a loose structure for the storage roots to expand. The cured and rooted slips should be spaced twelve to eighteen inches apart within these rows.
The planting depth is a factor in successful tuber development. Insert the slip deeply enough so that the entire stem, including at least two to three nodes, is buried beneath the soil surface. Only the top two or three leaves should remain exposed above ground. Planting the slip at a slight angle or horizontally along the mound is often practiced. This orientation promotes the formation of new roots along the entire buried length, leading to a higher yield.
Once positioned, gently firm the soil around the stems to eliminate air pockets. Immediate and deep watering is necessary to help the newly transplanted slips settle and begin establishment. The soil must be kept consistently moist for the first seven to ten days to ensure the young plants successfully root.
Ongoing Care and Harvesting
After establishment, ongoing care involves managing moisture and vine growth. While consistent moisture is needed during the first month, sweet potatoes become drought-tolerant once their root systems are developed. Deep watering during dry periods will improve the final yield. However, reduce watering in the final few weeks before harvest to prevent the tubers from cracking.
The sprawling vines cover the ground, which naturally suppresses weeds and conserves soil moisture. Do not frequently move or lift the vines once they begin to root at the nodes, as these secondary roots contribute to the final harvest. If the vines become overly expansive, they can be trimmed back sparingly to avoid reducing the plant’s ability to photosynthesize and feed the developing roots.
Sweet potatoes typically reach maturity between 90 and 120 days after planting, depending on the variety and climate. The most reliable sign of readiness is when the leaves and vines begin to turn yellow and die back, indicating the plant is shifting energy away from foliage. To harvest, carefully dig eighteen inches away from the main crown using a garden fork or spade, angling inward to loosen the soil and avoid damaging the tubers. Handle the harvested roots gently to prevent bruising and allow them to dry briefly on the soil surface before collection.