June 02, 2016
Transplanting
When you transplant a plant into the garden, the way you place it in the ground will influence the speed with which the roots of the plant will adjust to its new surroundings and how quickly it will become connected to the soil life web that helps feed the plant.
There are many different kinds of plants we transplant. Most are containerized, placed in a medium, usually composed of peat, bark and compost, and grown in plastic pots. These make handling easy but can contain hidden problems that should be dealt with.
Perhaps the most common problem is with plants that have grown for over a year in the container. Often you will find the roots thick around the outside and sometimes growing in a circle around the circumference of the pot. After pulling the plant out of the pot, examine the roots. If possible, gently tease the roots, separating them until they can all point outward, away from the center of the plant. After creating a hole that is as deep as the pot, spread the teased roots in the bottom of the hole and then cover with soil. This will allow the roots to grow outward and avoid creating strangler roots that can stunt or even kill a plant later.
Once the roots are spread, cover with a soil that has been amended with organic material such as compost and add a light sprinkling of materials such as blood meal and bone meal. These should be mixed into the soil that is being packed around the root ball. As the roots grow, they will be surrounded by a nutrient rich soil. Tamp this soil firmly enough to eliminate air pockets but gently enough so you don’t damage the roots. I often go around the plant, pressing with my heel on the circle of new soil. After a firm tamping the new soil, I gently press the outside of the root ball, being careful not to harm any stems or leaves.
Whether you are planting a hosta or an oak tree, it is wise to create a low dam in a circle around the site and fill this small crater with water. Let it soak then reapply. Wait then apply again. This is particularly important with large root balls such as those on big trees. A light watering will not saturate the root balls of such large trees and the initial watering is so important to give the tree adequate moisture to begin root and top growth. Keep watering into the summer, especially if the season is dry.
Another important factor is what is called textural continuity. If you are planting in a heavy clay soil you should avoid filling the planting hole with a light soil. The hole you dig can act like a pot, filling up with water in wet weather and drying out in dry weather. Once dry, it is often difficult to adequately rewet the soil mix. Refilling the planting hole with the same soil, although amended, is usually the best option.
Loose sandy or gravelly soils are not as critical, however it is still best to use a similar textured soil, but the addition of organic matter such as compost, rotted leaves or old manure will help maintain moisture and will provide nutrition in the coming years.
When planting large trees it is advisable not to dig a hole much deeper than the soil ball. Loose soil under the root ball will eventually compress downward and can leave the crown of the tree below the soil level. When this happens, the bark may become consistently damp and fungal diseases that cause crown rot may kill the tree.
The timing of transplanting is critical as well. If you are transferring a bare root plant, all will be well if the plant is dormant (buds are not expanded or in leaf). However, if you dig a plant in leaf, that plant will continue losing water through the leaves and it may wilt. Once this happens, it is unlikely it will recover. If you need to transplant while it is in leaf, cut the plant back very hard, at least to wood that has no leaves. This allows the roots to reestablish contact with the soil. Eventually new buds will emerge from the crown. Transplanting like this is not recommended unless there is no other choice.
Good soil, adequate tamping and watering, soil texture continuity and a good site are the prerequisites for success in transplanting. Without looking after these factors, the plant may remained stressed, often for many years. It may survive, but will rarely thrive.