Planting Trees Correctly to Ensure Their Success
Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist
Planting a tree isn’t as simple as digging a hole and sticking it in. Many trees fail to grow and thrive because they aren’t planted correctly. To determine just what is the “right” way to plant a tree, let’s look at some of the most common mistakes made when planting a tree or a shrub.
Probably one of the most common reasons for failure in planting trees and shrubs is that the root system is planted too deeply. Roots need air. They should always be planted at the same level or slightly above the level that they were growing in the nursery or in their container. Planting them deeper than this deprives the roots of air and will eventually kill most plants. Death is not usually a sudden thing. Trees planted too deep will fail to grow well. Leaves and new growth will be undersized. Leaves may develop leaf scorch along the edges or become yellow and drop off the tree. Keep in mind that trees aren’t tomatoes, most won’t tolerate deep planting.
Planting With Material Around the Root Systems
Any material around the roots... plastic twine, burlap, boxes, paper pots, and plastic pots should be removed at planting time. Most gardeners don’t have to be told to do this, but you’d be surprised at how many people belatedly find trees and shrubs planted with the roots still in a plastic pot.
Whether it’s a non-degradable material like plastic or a material such as paper which will eventually rot, it should be removed. Materials like cardboard boxes and pressed paper pots do rot, but they don’t rot quickly enough in our garden soils. They impede water movement and restrict root growth.
The same holds true for burlap. Even though burlap seems to rot readily it doesn’t rot as quickly as we would anticipate. Some burlap is even treated with a copper material to retard decay. Since copper is toxic to root tissues, the roots won’t grow through the burlap layer even if the burlap has decayed. In some instances, plastic burlap is used. That definitely won’t decay any time in the near future.
Dense Root Masses and Encircling Roots
When left growing in containers too long, many trees and shrubs develop cramped root systems, which make it difficult to grow them with success. For plants to survive and grow, you will need to loosen the roots of those with dense, fibrous root systems. When roots are dense and matted, cut them with a shovel, spade, or knife. Make six to eight shallow vertical cuts into the exterior root mass. Use your fingers or a hand fork to loosen the cut roots and help spread them out.
Another method of remedying problems with dense root masses of container grown plants is to “butterfly” the bottom of the root mass. Use a shovel or spade to divide the bottom half of the root mass, creating two flaps or “wings.” The “wings” are kept apart by with soil, a stone, or a stick before filling the planting hole with soil. Make six to eight vertical cuts to the exterior roots in the uncut, top portion of the root mass.
Plants with thicker, woodier roots, often develop encircling roots when grown in a pot too long. These roots will keep growing in circles, if they aren’t disturbed at planting time. The roots should be cut and spread as just described above. With encircling roots the plant eventually chokes itself to death. Circling roots can’t reach out in the soil for water and nutrients needed for healthy growth and the poorly established root system doesn’t perform its anchoring function very well.
Clay Root Balls
Many quality nursery plants sold in this area are dug from nursery fields in the Williamette Valley in Oregon. Many of these fine plants have one major drawback... the soil in the root ball is a heavy clay. This clay is very different from local yard and garden soils. It’s dense and holds onto water very tightly. When the landscape is watered to accommodate our lighter, more droughty soils, the plant ends up with roots that are constantly too wet because of the clay soil around the roots -- this often leads to root rots.
One can avoid the problem by avoiding the purchase of plants with clay soil or one can try to remedy the situation by gently forking soil away from the root system and exposing the roots.
Creating a Bathtub Effect
Adding organic matter such as peat moss, compost, or mulch to the backfill soil of a planting hole is not a good. It generally is not helpful and can create a “bathtub” effect. Water easily enters the coarser soil in the planting hole but drains our slowly because the surrounding soil is more dense. Again, the roots stay wet for long periods of time and root rots are very likely to develop.
However, when planting an entire landscape bed or border amending the soil with organic matter is a good idea. Loosening the soil and adding the organic matter fosters good root growth. Preparing the soil in the entire bed for planting eliminates the bathtub effect that can occur with planting holes.
In planting sites around new homes and buildings, the soil is often very compacted. This is especially true on commercial sites where the soil had been compacted with heavy machinery to provide a suitable area for paved parking. Roots of trees, shrubs, and other plants have a hard time growing in compacted soil. Water doesn’t move well into and through compacted soil. There isn’t as much oxygen available to plant roots in a compacted soil. Because the soil is tight, roots have a hard time penetrating the soil.
The best thing that can be done in a new planting area to relieve soil compaction is to loosen the soil by physically disturbing the soil by deep tilling or digging.
Proper Planting Techniques
- Dig the hole deep enough to accommodate the root ball. Keep in mind that the top of the root ball should be level with the soil or slightly above it. The planting hole should be at least twice the diameter of the root ball. The wider the hole, the better. Note: Always lift your tree and shrub by the root ball, not by holding onto the trunk.
- For balled and burlapped plants, first situate the plant in the hole and then remove all twine, string, or wire from around the root ball and stem. Cut the burlap away from the root ball, removing as much as possible from the hole. For container-grown plants, cut and loosen roots if needed before placing the root ball in the hole.
- Add appropriate amounts of slow-release nitrogen fertilizer to the planting hole. Backfill with the native soil you removed from the hole. Do not amend the backfill soil with organic matter. Gently firm the soil around the roots and definitely don’t tamp the soil down around the roots with your feet.
- Water the plant thoroughly to help settle the soil around the roots. Mulch the entire root zone area with bark mulch.
- Keep the soil around the roots moist but not wet and saturated.
- Prune to remove only the broken branches.