Plants often grow together due to self-seeding, aggressive root spread, or being planted too closely, leading to overcrowding. This dense growth forces individual plants to compete intensely for resources like moisture, nutrients, and sunlight, resulting in stunted growth, fewer flowers, and a weakened appearance. To restore plant health and encourage vigorous new growth, gardeners must separate the intertwined root systems and create new divisions. The following methods provide practical steps for safely separating these plants, ensuring a high rate of survival for the new transplants.
Essential Preparations Before Digging
Selecting the correct time for separation minimizes stress on the plant. Most established perennials and shrubs are best divided during their dormant or least active periods. This allows them maximum time to establish new roots before the next growth or bloom cycle begins. Spring- or summer-blooming plants are typically divided in the early fall, about four to six weeks before the first hard frost. Fall-blooming plants should be separated in the early spring as new growth first emerges.
Proper hydration is a prerequisite for a successful transplant operation. The plant should be thoroughly watered one to two days before separation to ensure root cells are resilient against disturbance. Before digging, gather a sharp spade, a garden fork, a sturdy knife, a tarp or wheelbarrow, and a watering can. Ensure all cutting tools are clean to prevent pathogen transmission. Finally, prepare the new planting site first, ensuring the hole is ready so divisions can be replanted immediately and their exposed roots do not dry out.
Dividing Established Root Clumps
The process for dividing mature, clump-forming plants, such as ornamental grasses, hostas, or hardy perennials, begins with careful excavation. Use a sharp spade to cut a circle into the soil several inches outside the plant’s drip line (the outer edge of its foliage) to capture the root ball. Digging wide rather than deep minimizes damage to the root system. Gently rock the spade or fork to loosen and lift the entire root mass from the ground. Once the clump is out, place it onto a tarp, and gently shake or brush away the excess soil so the root structure becomes visible.
With the roots mostly exposed, identify the natural division points where the crown can be separated into smaller sections. Each section must contain healthy roots and at least one or two growth buds or shoots. For plants with loosely matted roots, like yarrow or creeping phlox, the clump can often be gently pulled apart by hand. Densely packed or woody crowns, such as those found on daylilies or thick ornamental grasses, require mechanical force for separation.
To divide a tough root mass, insert two garden forks back-to-back into the center of the crown and use the handles as levers to pry the sections apart. Alternatively, a clean, sharp knife, a soil knife, or a sharp spade can slice directly through the crown. Ensure each resulting section has a viable root system. Immediately after separation, cover the divisions or place them in a bucket of water to prevent desiccation, as root exposure to air and sun is the most common cause of transplant failure.
Separating Delicate Seedlings and Annuals
Separating young, fragile plants, such as vegetable starts or densely self-sown annuals, requires a gentler approach compared to dividing mature root clumps. The goal is to minimize root disturbance and avoid crushing the tender stems. Start by thoroughly soaking the entire root mass in a container of water for a few minutes to soften the soil and make the roots more pliable.
Once the soil is saturated, carefully tip the container and gently slide the tangled root mass out. The “wet separation” method is effective: gently massage the saturated soil away from the roots while submerged in water, allowing the individual root systems to untangle. When handling young plants, always grasp them by their leaves or cotyledons (the first embryonic leaves). Avoid touching the delicate stem, as damage there is often fatal.
For small or extremely intertwined seedlings, a fine tool like a toothpick, a plant label, or sterilized tweezers can gently tease the roots apart. Work quickly to keep the exposed roots moist and avoid prolonged exposure to air. The newly separated seedlings should be immediately moved into their individual pots or planting sites, ensuring they are replanted before the fine root hairs dry out.
Successful Replanting and Aftercare
Before placing the newly separated divisions into their final location, inspect the roots. Use clean shears to prune off any roots that are severely broken, torn, or overly long, as this encourages the rapid development of new feeder roots. The new planting hole should be dug two to three times wider than the root ball but no deeper, allowing the roots to spread easily into the loosened soil.
Place the division in the center of the hole, ensuring the crown (where the stem meets the roots) is level with or slightly above the surrounding soil grade. Backfill the hole with soil, tamping gently to ensure good root-to-soil contact and eliminate air pockets that can dry out roots. Immediately after planting, water the division deeply; this settles the soil around the roots and provides the necessary hydration to begin recovery.
To mitigate transplant shock (a temporary wilting or slowing of growth), provide temporary shade for the first week, especially during the hottest part of the day. Maintain consistent soil moisture without waterlogging. Delay the application of high-nitrogen fertilizers for two to four weeks until new growth indicates the plant has successfully established its root system.