In their natural environment, tree seedlings grow under the protective shade of the forest. There, lower light intensities, higher humidity, and reduced air movement combine to reduce stress on the young plants.
These seedlings are extremely vulnerable when transplanted, needing to overcome the shock of transplanting and re-establish roots in new soil conditions as well. In the new environment they also may be exposed to damage caused by wild animals such as deer, livestock and even man-made depredations including trimmers and mowers, or possibly salt spray from nearby highways.
To simulate the supportive conditions of light, humidity and other factors, growers have employed tree tents, or tree shelters. This is not a new technique; tree farms have used tents for more than 30 years. That does not mean, however, that both technology and techniques have not changed.
“Agroforestry is extremely important in creating more diverse, productive, profitable and sustainable land,” said Joel Gamboa, technical sales with Tubex. He adds that agroforestry also encourages biodiversity and provides habitats for pollinators and predators.
Read more: Management material
“Protecting trees during the establishment period is important and tree shelters allow growers flexibility in how they establish trees and manage their land,” Gamboa said.
Once known as Tuley Tubes, wrapping began in England in the late 1970s. Forester Graham Tuley showed that wrapping polyethylene around nylon mesh tree protectors caused a greenhouse effect that made trees grow faster.
These shelters are solid or mesh structures designed to protect seeds, seedlings or recently transplanted trees from various types of damage due to weather conditions or animals in the forest environment. The shelters can be made of various materials and are available in tubular (round), square, triangular or hexagonal shapes. As yet there seems to be no clear consensus as to a preferred type.
These sheltering tools are most commonly available in translucent polyethylene or polypropylene, sometimes double-walled for additional strength, and also in mesh, depending on the environment where they will be used.
Traditionally, shelters are held in place by stakes, driven into the ground next to the young tree. Stakes may be integral with the shelter, or a separate piece. Depending on need, bird netting may also be necessary at the top of the shelter.
Songbirds are often a nuisance, because they perch on shelters and can damage emerging shoots as well as restrict terminal growth of the trees as shoots reach the tops of their shelters. This netting can also prevent birds from falling into the shelter, becoming trapped and dying. It also reduces damage from Japanese beetles, along with wasp and bee nest formation.
In addition, a woodlot operator must pay attention to the possibility of damage by rodents such as voles, mice and rabbits. To prevent gnawing at the base of tender seedlings, shelters must be firmly snug to the ground. Rodents may even use the shelters as protection from their natural enemies.
Netting needs to be removed as the seedlings grow so as not to deform the stem.
Tree shelters help reduce the need to control other vegetation, which can compete with the seedlings for moisture and nutrients.
Although weeds and grasses around the seedlings may not be a major problem, the fact that they are native to the site means they are more vigorous and aggressive than the seedlings. Thus, they can decrease seedling growth and reduce the effectiveness of the shelters. Where controlling the surrounding vegetation is necessary, shelters can also protect seedlings from herbicide applications.
Shelters provide wind protection for seedlings by not only reducing water movement through the plant (transpiration) but also increasing the relative humidity inside the shelter. Wind can, however, knock over the shelter and kill the still-delicate seedling. This makes the secure staking of the shelter very important, additionally guarding against the shelter leaning onto and damaging the plant.
Read more: Protecting woodlots from fire damage
The shelter shape, according to various studies, has little effect on seedling growth. The height of the shelter, however, can be important where there is danger from browsing deer. If deer are an issue, the tree tent should be at least 4 feet high.
Additionally, some shelters are designed with a flare at the top to allow for the maturing tree’s growth. Those available from Tubex, for example, have a laser line in the plastic that allows for the shelter material to break away as the tree grows.
Keith Misukanis, sales and marketing director for Avintiv, said, “We’re still working on the correct amount of airflow [to benefit seedlings]; it depends on the area, southern exposure, etc.”
Shelter diameters of 4 inches have been shown to be adequate for seedling maturation, while larger diameters have been shown to diminish shelter benefit. Smaller diameters – less than 3.5 inches – may cause the leaves to bunch up, making the shelter crowded and potentially stopping leaf production, affecting growth and stem formation.
Climate and the environment will affect the shelter’s durability and life expectancy. Growers should select a shelter that provides the best “micro” environment for the seedling. Polyethylene offers the advantages of strength and nontoxicity and can decompose over time. PVC pipe, which doesn’t degrade quickly, can also be used for shelters.
List of Tree Shelter Suppliers
This list of tree shelter suppliers is not meant to be exhaustive but is representative of the tree tents and similar product offerings available.
- McKnew Enterprises, P.O. Box 2128
Elk Grove, CA 95759
- Summit Environmental Group, P.O. Box 12267
Toledo, OH 43612
- Terra Tech, P.O. Box 2128
Eugene, OR 97405
- Tree Pro, 3180 West 250 North
West Lafayette, IN 47906
- Treesentials Company, 60 E. Plato Blvd.
Saint Paul, MN 55107
The USDA Natural Resources Conservation Services of North Dakota offers an online fact sheet on Tree Shelter Installation and Maintenance.
Other recently published literature includes Tubex’s “A Guide to Agroforestry.”
Costs to consider
Shelters are a major cost consideration in re-foresting plans, so they should be used on high-value species (such as red oak and black walnut), and those that are hard to establish or are especially attractive to foraging deer.
Material and labor are important costs to consider. Installation of shelters is an early cost, but ongoing maintenance, weeding and checking on the installation also need to be considered. Reusable shelters can decrease the cost of the operation.
An older study of reforestation efforts in the Allegheny National Forest in Pennsylvania summarizes that interest in the use of tree shelters has increased sharply, citing the shelters’ protection of natural and planted seedlings from deer browsing, as well as their promotion of both survival and height growth.
More recently, research has shown that selecting valuable species for the use of shelters can make the investment more effective.
In addition, there are governmental programs that provide financial assistance for tree planting, such as the deduction of reforestation costs from federal income tax.
Read more: Making the woodlot work