Transplanting trees can be a risky – and costly – business.
That’s why a tree care duo from Ithaca, N.Y., is urging green industry professionals to consider alternatives to the typical bag and burlap approach often used to relocate street trees. Specifically, Nina Bassuk, urban horticulture professor at Cornell University, and Andy Hillman, city forester for the City of Ithaca, NY., favor the bare root tree-planting method.
But what, exactly, does the alternative technique entail?
“Bare root trees are those dug and stored without any soil around their roots,” Bassuk explains. Rather than using a tree spade to uproot and remove trees, the bare root method means digging them from their homes and shaking off excess soil. Once removed, bare root trees are dipped in a hydrogel slurry to preserve the exposed roots until transplantation is complete.
The hydrogel solution helps a tree hold up to 400 times its weight in water, preventing desiccation of the roots during relocation. The slurry mixture is a synthetic water-absorbing compound with a consistency similar to that of thick gravy. Generally, bare root trees should be soaked in the solution for 12 to 24 hours.
Once a tree has been removed and dipped in the slurry, its coated roots are wrapped in large, pleated plastic bags for safe storage until the tree’s new home is prepared for planting. Bare root trees can stay in the plastic bags for seven to 10 days so long as they are kept cool.
Ithaca, N.Y., provides an ideal setting for experimentation with tree-transplanting methods. The small city boasts a total of 8,000 street trees and 3,000 park trees – representing 391 different species codes.
“Ithaca is the most diverse urban forest in the northeast,” Hillman comments. And the city is proud of its bare roots approach to planting.
Bare Root Benefits. Since bare root trees are not pulled from the ground with the help of tree spades, they generally maintain fuller root systems than those removed via other means – namely, the method of balling and burlapping roots, which Bassuk and Hillman refer to as “B&B.”
Using a tree spade usually takes off about 90 percent of a tree’s root system, Bassuk observes. That can create problems, since larger root systems provide more opportunities for the tree to take in water for growth.
“Studies show that 200 percent more root volume is saved by using the bare root method than the typical B&B system,” Hillman comments.
The B&B approach results in much heavier trees as well, which means more work and space for transplanting. Thus, the bare root approach also can save money, since the lighter weight trees can be lifted and planted by volunteers – instead of professionals.
Bare root trees are easy for unskilled volunteers to plant without the aid of hefty equipment, since they are so much lighter than those transplanted using the B&B method. Although weight obviously varies from tree to tree, Bassuk ventures that bare root trees weigh approximately 25 or 30 pounds each – considerably less than B&B trees, which can range from 150 to 300 pounds apiece.
Shipping the bare root trees is less expensive as well because more plants can fit on a truck. Specifically, Bassuk notes that using the bare root method can save 30 to 50 percent when it comes to shipping. Add to that the savings related to planting with unpaid volunteers, and the overall price difference is substantial.
Another benefit to the bare root method is increased accuracy in planting depth. “A problem we’re seeing more and more is planting trees too deep – or mounting too much soil on top of the roots,” Bassuk says. “This often happens with the balled and burlapped trees because the roots are compacted when they are planted. But with the bare root method, the trees don’t get planted too deep because you can easily see the root flair.”
A tree’s root flair is the area where the roots start spreading out from the trunk and often is covered by the dirt ball in which the tree was packaged. The planting hole should be just deep enough to keep the flair above ground level.
Also, professionals who opt for the bare root method don’t have to deal with soil textural interface – which means that since a bare root tree does not carry soil to its new location, there are no worries about matching soil conditions from the former site to conditions at the tree’s new home.
Bad New for Bare Roots. Not everyone is in favor of the alternative tree-transplanting method recommended by Bassuk and Hillman.
Opponents of the bare root method argue that bare root trees have trouble standing up to excessive wind – since their roots are not entrenched in the new soil enough to stay upright. However, Hillman says staking the trees is an obvious remedy.
Another concern about bare root planting is the narrow planting window. Since bare root trees require adequate soil moisture for successful results, mid-spring and mid-fall are the two ideal planting periods.
Also, some species, including hawthorn, hornbeam, shingle oak and gingko, do no perform well when moving with bare roots. English oak, honeylocust, sugar maple and red oak trees are a better bet for the alternative method.
Click here for more information about the bare roots method and its implementation in Ithaca, N.Y.
The author is assistant editor-Internet of Lawn & Landscape magazine and can be reached at aanderson@lawnandlandscape.com.