Plant division is a technique of asexual propagation used to create new, genetically identical plants from a single parent specimen. This process involves physically separating the plant’s root mass and crown into smaller sections, each capable of growing independently. Division serves a dual purpose: it increases the number of plants and maintains the health and vigor of mature, clumping specimens. Plants that are root-bound or severely overcrowded often show reduced growth, diminished flowering, or a “bald spot” in the center, signaling they are ready for separation.
Identifying Suitable Plants and Preparation
The most appropriate candidates for division are plants with a fibrous or clumping root system, such as herbaceous perennials, ornamental grasses, and certain houseplants like hostas, daylilies, and ferns. These types naturally form multiple crowns or offsets that can be easily separated. Plants with a single, deep taproot, like milkweed or false indigo, are generally unsuitable, as disturbing the main root often causes irreparable damage.
The optimal time for division is when the plant is not actively growing or flowering, allowing its energy to focus on root establishment. This usually means early spring before new growth begins, or in the fall after the foliage dies back, ideally four to six weeks before the first hard frost. Water the mother plant thoroughly one to two days in advance to minimize transplant shock and make the root ball easier to handle. Essential materials include new pots, fresh potting mix, and a clean, sharp cutting tool (knife or spade) sterilized with rubbing alcohol or a bleach solution to prevent pathogen transfer.
Techniques for Separating the Root Mass
Begin the division process by carefully removing the plant from its container, perhaps by gently tapping the pot’s sides or running a knife around the interior edge. Once the root ball is free, gently shake off or wash away excess soil to expose the root structure and identify natural divisions or distinct crowns. For plants with loosely bound or fibrous roots, such as grasses or spider plants, you can often gently tease and pull the clumps apart by hand.
For plants with a dense, matted, or woody root mass, a more assertive approach is required. Use a sterilized sharp knife, serrated blade, or spade to slice cleanly through the root ball, separating it into sections. For tough root masses, such as mature daylilies, inserting two garden forks back-to-back and using them as levers can split the clump without excessive tearing. Each separated division must retain a healthy portion of roots and at least one viable growing point (stem or crown). Discard any old, dead, or woody center portions of the original plant, as these areas are less vigorous.
Repotting and Post-Division Care
After separation, the divisions must be promptly replanted to prevent the root hairs from drying out. Select new pots only slightly larger than the divided root mass; an overly large container holds excess moisture and can lead to root rot. Fill the pots with a high-quality, well-draining potting medium, ensuring the plant’s crown—the junction between the roots and the stems—sits at the same soil level as before.
Once positioned, backfill around the roots with the fresh mix, lightly pressing the soil down to eliminate air pockets. The first watering is important: saturate the soil thoroughly until water drains from the bottom. This settles the potting mix around the roots and provides immediate hydration. To minimize transplant shock, place the newly potted plants in a protected location that receives bright, indirect light, avoiding harsh, direct sun for the first few days. Maintain consistent soil moisture, checking the top inch or two for dryness before watering again. Refrain from applying fertilizer for at least four to six weeks to prevent burning the recovering root system.