After a long season of gardening, most of us are ready to hang up our shovel and head for the porch. Not so fast! Fall is the optimal time to plant trees and shrubs. The heat stresses of summer are past, and water needed to support a growing root system is more regular and abundant. Roots will grow until the subsurface soils go below 40° F.
But before taking shovel to ground make sure you’re up to date with research-based planting practices:
- “Dig a $50 hole for a $5 tree”? Those days are past. New research shows that trees and shrubs grow better in holes that are the depth of the root ball and slightly wider. When planted in deep holes with backfill underneath, the soil settles over time and plants sink and end up too low. Compacted soils should be addressed in the entire area that the plant roots will inhabit, rather than in a wide planting hole. Amendments should not be included in the backfill. The plants will ultimately grow in the native soils, and their long-term health is better when they are initially planted in these soils. If a soil test indicates that amendments are required, the soil should be amended in the entire area the mature root zone will inhabit.
- Give some attention to the root ball. Correcting girdling and circling roots and determining the location of the root flare (the area where the topmost roots extend outward) are essential. Many researchers suggest practicing “root washing”—soaking the root ball and then rinsing away the soil and amendments. This allows a close inspection of the root system. Problem roots can be pruned, girdling roots can be straightened, and the root flare clearly seen.
- Which leads to a critical best-practice. Trees and shrubs must be planted so that the root flare is at or slightly above (for settling) ground level. Too high and the root system will dry out. Too low and the plant will not have access to needed oxygen. Trees may take years to display decline—an unhappy surprise when a tall tree shows stress symptoms from improper planting.
- Then there’s staking. Tree lovers love to stake their newly planted trees. Unfortunately, young trees that do not have the ability to bend with breezes do not develop as quickly. The movement of their trunk helps trees increase caliper. Of course, staking needs to occur in some situations—top heavy structure, sparse roots, etc.—and when it is necessary, the attachment to the stake should be loose and in a figure eight.
- After backfilling the planting hole, do not stomp on the soil to settle it, which removes the small spaces that store oxygen and water. Water the plant well to remove large air spaces and give the tree or shrub the moisture it needs for a good start. During the first year, water well when the soil is dry, about an inch a week.
- After planting, mulch the planting area with 2-4” of good quality bark or wood chips, but keep the mulch from touching the tree or shrub trunk (which can lead to disease and foster pest entry). The mulch will need to be renewed, which is a good thing—as it breaks down, it adds organics and microorganisms to the soil.
- Do not fertilize trees or shrubs unless a soil test or foliar evidence indicates the need.
Many of these new practices go against our gardening instincts. We love our trees and shrubs and want to pamper them, stake them, and provide the best of nutrients. Dr. Ed Gilman (University of Florida) and other researchers have provided good data showing that the above practices result in better and healthier tree (and shrub) growth. “Less is more” could be the new mantra for shrub and tree planting.
PROBLEMS WITH PLANTING TREES: Dr. Jim Downer, University of California Extension
https://gardenprofessors.com/problems-with-planting-trees/
THE MYTH OF SOIL AMENDMENTS: Dr. Linda Chalker-Scott, Puyallup Research and Extension
Center https://s3.wp.wsu.edu/uploads/sites/403/2015/03/soil-amendments.pdf
WHY ROOT WASHING IS IMPORTANT: AN ILLUSTRATED CAUTIONARY TALE: Dr. Linda
Chalker-Scott, Puyallup Research and Extension Center https://gardenprofessors.com/why-root-washing-is-important-an-illustrate...
NOTE: Plants that are marginally hardy (crapemyrtles, butterflybush, etc) are better planted in the spring. Conifers planted in fall benefit from an antidesiccant spray to protect them from drying out during winter winds.
–Karen Edgington, Master Gardener Volunteer