Container Grown Trees and Shrubs: Fix Those Roots Before You Plant

Years ago, trees and shrubs were dug up and transplanted to a new location or shipped by nurseries with bare roots while they were dormant (not in leaf). This system of transplanting worked well if the roots were kept moist and as long they were planted quickly before they broke bud. 

Today most of the shrubs and many small trees are being grown in light plastic containers at nurseries around the country. This allows us to move and transplant these plants almost anytime throughout the growing season, extending our ability to plant landscapes later into the summer. The shrubs and trees are grown in a soilless media such as pine bark and perlite and constantly irrigated in the nursery (often drip-irrigated) to increase growth and keep the plants alive. Containerized plants do not require the labor-intensive digging that bare root or balled and burlap plants require before plants break bud. They also do not leave roots behind during a digging process and undergo transplant shock due to loss of roots.

Containerized plants sound great, but there are several problem conditions that can cause root problems and the death of your new plants. The first major problem has to do with growing a root system in a small pot. Tree and shrubs will quickly grow large root systems that hit the sides of the container and turn. Within no time the container is full of circling roots and the plant becomes pot bound. Several years after planting, these circling roots will begin to girdle or strangle the stem or trunk, ultimately killing the tree or shrub.

The next issue is the soilless media that quickly dry out when planted in a landscape that soon becomes hot and dry. The plant's root system that was used to be irrigated in a nursery, is now under stress and drying out after transplanting into soils. Because containerized plants have 100% of its root system, they quickly struggle to survive if they are not irrigated, so make sure you are watering container-grown trees and shrubs.

The last concern involves the depth of the stem and root system in the container. All too often the trees or shrubs are planted a little bit deep in the container. This causes more root defects and when planted deeper in a landscape the root system often adjusts by growing up and then circling or girdling the stem with time.

Preventing or correcting these problems is not that difficult, but needs to be done. First, examine the root system of the plants you are about to purchase. Pull them out of the container and look to see if it is "pot bound" and already has many circling roots. If so, you might want to look for another plant. You can also ask the nursery if they are using new containers that air-prune roots, or container painted with SpinOut, a copper hydroxide solution that reduces circling root.

Once you have purchased containerized trees and shrubs, be prepared to cut and manipulate roots before you plant it. Research has shown that it is best to sever roots with a sharp utility knife or handsaw or even a sharp spade. Even shaving the sides of the container-grown root system with a handsaw works well to remove the circling roots that formed at the edge of the container. Don't worry, this won't really hurt the plant. It has 100% of its root system unlike bare root and balled and burlapped production that leaves many roots back in the nursery when dug. Studies show that the roots that are cut regenerate quickly and grow into the landscape soils, helping the plant get established and survive dry spells.

For more information contact your local Extension Office or visit Planting and After Care of Community Trees.