Though trees and shrubs can be planted or transplanted whenever the ground isn’t frozen, cool air and warm soil temperatures make autumn the best time to do the job.
The cooler air is kind to plants and trees, especially those that have just lost a major portion of their roots during digging. Soil temperatures are still warm, creating an excellent environment for new root growth.
Many plants and trees are entering a period of dormancy, so energy normally required to sustain foliage can go into root development and storing nutrients and resources during the cool months. By the spring, when demand for new growth above ground starts again, the root system should be well established so the plant can handle the upcoming demands of summer.
Here are a few additional tips to ensure the success of all your fall transplants.
• When transplanting, advance work can make the difference between those trees and shrubs just surviving and thriving. Make the planting hole two to three times wider than the current root ball, but no deeper than the plant was growing in its previous environment.
If you’re planting a container-grown plant, don’t assume that the soil level in the container indicates the proper depth for planting. Many times growers add more soil to the container, ultimately putting too much above the root level. At planting time, scratch away the soil to find where the roots really start. That’s the proper level for planting in the ground.
It is better to plant a tree or shrub slightly high and allow the area to drain than for a plant or tree to sit in a “bowl” and collect excess water. Newly disturbed soil has a tendency to settle, and plants growing below grade can easily succumb to root rot or disease.
• When backfilling, return the existing soil to the planting hole around the roots, without amending the soil. The latest research indicates that roots growing in amended soil rarely venture into the harder native soil. For best long-term establishment, break up the existing soil, remove the rocks and backfill.
• A critical step at this stage is to water well. Not only does it provide needed moisture but the water also helps eliminate air pockets that could result in dead roots.
The final step is to mulch with 3-4 inches of organic matter, such as shredded leaves, ground bark or straw. Mulch helps soil retain its moisture and moderate its temperature. Winter can bring dry conditions, so water if needed. Roots are still growing and soil moisture is essential.
Joe Lamp’l is host of PBS’ “Growing a Greener World.” Reach him at joegardener.com.