The term “potato slip” refers to the specific propagation method used for growing sweet potatoes (Ipomoea batatas), not the common white or Irish potato. As a tropical root vegetable, sweet potatoes require a unique starting process compared to their temperate relatives. Using slips ensures a successful start for these heat-loving plants in most climates.
Defining the Sweet Potato Slip
A sweet potato slip is a young, vegetative sprout that emerges directly from a mature sweet potato tuber. These sprouts are small vine cuttings that develop into new, genetically identical plants. The slip starts as a shoot with a few tiny leaves and forms adventitious roots along the stem. Gardeners harvest these rooted sprouts to transplant them into the garden.
The use of a slip differs from propagating the common potato (Solanum tuberosum). Traditional potatoes are grown from “seed potatoes,” which are pieces of a tuber containing at least one bud. Planting a whole sweet potato directly into the soil often results in poor growth or rotting, especially in cooler climates. The slip acts as a clone of the parent plant, ensuring consistent traits and yield.
Step-by-Step Guide to Creating Slips
The process for generating sweet potato slips begins indoors, approximately six to eight weeks before the intended outdoor planting date. Start with a healthy, cured sweet potato, ideally an organic one, since conventionally grown tubers may have been treated with sprout inhibitors. To induce sprouting, the tuber must be provided with warmth and moisture.
There are two primary methods for inducing slips. The water suspension technique involves suspending a whole sweet potato halfway in a jar of water using toothpicks. Ensure the rooting end is submerged. Alternatively, the soil method involves laying the tuber horizontally in a shallow container filled with moist potting mix or sand, covering the sweet potato about halfway. Both methods require keeping the tuber consistently moist in a warm environment, ideally 70 to 80 degrees Fahrenheit, which encourages rapid slip development.
Place the container in a sunny window or under a grow light to provide the necessary light for the developing shoots. Over the next few weeks, sprouts will emerge and grow leaves. Once the shoots reach about six to eight inches long and have developed several leaves, they are ready to be harvested from the parent tuber.
To harvest a slip, gently twist or cut the sprout off at its base where it meets the sweet potato. Cut the slip about an inch away from the mother potato to avoid transferring potential plant diseases. These detached slips are then placed in a jar of water, submerged at the base but keeping the leaves dry, to encourage a strong, fibrous root system. Roots typically develop quickly, and the slips are ready for planting once the roots are several inches long.
Planting and Initial Care for Slips
Successful outdoor planting depends entirely on soil temperature, not just the calendar date. The soil must be consistently warm, ideally reaching at least 65 to 70 degrees Fahrenheit, which usually occurs about a month after the last spring frost. Planting too early in cool soil will stunt the young plants or cause them to rot.
Before planting, prepare the garden bed by creating raised rows or hills, approximately eight inches high. This helps the soil warm up faster and ensures better drainage. Space the plants 12 to 18 inches apart in rows at least three feet apart to provide room for the sprawling vines. When transplanting, bury the rooted slip deep enough so at least two nodes—the points where leaves emerge—are covered by the soil, leaving a few leaves above the ground.
Immediately after planting, water the slips thoroughly and keep the soil moist for the first week to help them establish root systems. If the sun is intense, providing temporary shade for the first few days can prevent wilting. Once established, the plants’ vigorous growth will quickly shade out weeds. Consistent moisture, about one inch of water per week, will help ensure a larger, crack-free harvest.
Why Slips Are the Preferred Method for Sweet Potatoes
Sweet potatoes are propagated using slips because this asexual reproduction method maintains the desired characteristics of the parent plant. Since the slip is a genetic clone, the new plant produces tubers identical in flavor, color, and texture to the mother sweet potato. This genetic consistency is paramount for both commercial agriculture and home gardeners growing a specific variety.
Reproduction via true seeds is impractical because the flowers often do not produce viable seeds, especially in temperate regions. Even when seeds are produced, the resulting plants exhibit genetic variation, leading to unpredictable tuber characteristics. Using slips also aids in disease management, as the shoots are cut from the mother tuber, reducing the likelihood of transferring tuber-borne pathogens directly into the garden soil.