Repotting, often called “pricking out” or “potting up,” is the process of moving a young plant from its initial, crowded seed-starting environment into a larger container. This staged approach allows the seedling to continue growing indoors until it is robust enough for outdoor life. The primary purpose is to provide the expanding root system with more space, fresh nutrients, and greater soil volume. Moving a seedling at the correct time prevents growth stagnation and encourages the development of a healthy, vigorous plant.
Assessing Seedling Readiness
The timing for repotting is signaled by specific visual and structural cues. The most reliable indicator is the appearance of the first set of “true leaves,” which are distinct from the initial, smooth, embryonic leaves called cotyledons. Cotyledons are the first leaves to emerge, providing the seedling with stored energy until photosynthesis begins. True leaves, by contrast, resemble the mature plant’s foliage, often having ridges or serrated edges, and signify the start of active nutrient production.
Another sign that a seedling is ready is the development of its root system. If the seedling is gently lifted from its cell, the roots will hold the soil plug together, maintaining the shape of the original container. Roots poking out of the drainage holes or forming a dense, white, circling mat around the soil plug indicate the plant is “root-bound.” Waiting too long causes the plant to become stressed, resulting in stunted growth or “legginess,” where the stem is long and weak. Repotting when the first one or two sets of true leaves have developed ensures the seedling is strong enough to handle the move.
Gathering Supplies and Potting Mix
Having the necessary materials ready minimizes the time the delicate roots are exposed to the air. The new container should be only slightly larger than the old one, typically moving from a seed-starting cell to a pot about two to four inches in diameter. This proportional increase prevents the roots from sitting in excessive, unused soil, which can retain too much moisture and lead to root rot.
The potting medium should be a sterile, well-draining mix, often a premium potting soil formulated for general container use. Seed-starting mixes are often too nutrient-poor for this stage of growth, while garden soil is too heavy and may contain pathogens. Tools like a small trowel, a dibbler, or a simple spoon are useful for creating a planting hole and gently handling the soil. Pre-moistening the potting mix before planting ensures immediate moisture availability for the roots.
Step-by-Step Repotting Technique
Prepare the seedling for removal by lightly watering the original cell a few hours beforehand to loosen the soil. To extract the seedling, avoid pulling on the stem, which can cause irreparable damage to the vascular system. Instead, use a tool like a fork, spoon, or dibbler to gently lift the soil plug from underneath, supporting the seedling by a leaf or the soil itself.
Once removed, inspect the root ball. If the roots are tightly matted or circling, gently tease them apart with your fingers or a small tool to encourage them to grow outward. The new pot should be partially filled with the pre-moistened soil mix, and a depression created in the center to receive the root ball. Place the seedling into this hole, ensuring the roots are spread out rather than clumped.
The correct planting depth is species-dependent. For most plants like lettuce or brassicas, the seedling should be placed at the same level as it was in the old container, matching the existing soil line. However, leggy seedlings (particularly tomatoes and peppers) benefit from being planted deeper, as they can grow adventitious roots along the buried stem. After positioning the seedling, gently fill the remaining space with soil, lightly firming it around the base to eliminate any air pockets.
Essential Post-Repotting Care
Immediately after the transfer, the newly repotted seedling requires careful attention to minimize “transplant shock.” A gentle but thorough watering is the first step, as this settles the new soil around the roots and ensures root-to-soil contact. This initial watering is crucial for recovery.
The seedling should then be placed in a slightly shaded location or under less intense light for the next 24 to 48 hours. This temporary reduction in light intensity allows the roots to begin establishing themselves before the leaves are forced to support a high rate of photosynthesis and water loss. Monitor the plant closely for signs of wilting, which indicates that the roots are struggling to absorb water. Once the seedling appears stable and upright, it can be returned to its normal, brighter growing conditions, and the regular watering and feeding schedule can be resumed.