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More production method and transplanting information

See: update on percent roots harvested in root ball

1) Field grown vs. fabric container grown: Root balls of field-grown trees are similar to those grown in fabric containers (click here for photo comparison) except that fabric container-grown root balls are about half the volume (Gilman et al 1992;Gilman and Beeson 1996). This makes them easier to handle. Research now shows that about the same percentage of roots are harvested from both production methods (Gilman, et al, 1992; Gilman and Beeson 1996; Harris and Gilman 1991). Because the root ball is smaller, there is less water storage capacity in the fabric container root ball than in the larger-sized root ball of the field-grown tree. Combined with a dense root system, this lesser reserve makes trees produced in fabric containers more sensitive to desiccation immediately after digging than trees grown directly in field soil. Quality nursery operators make provisions for delivering the irrigation needed to prevent desiccation immediately after harvesting.

Trees produced in fabric containers are as viable in the landscape as those grown directly in the field if they are handled carefully and irrigated properly after digging (Hensley 1994; Gilman and Beeson 1996). Many growers harvest trees from these in-ground fabric containers and transplant them into above ground containers to root out. Then they are sold as container trees. When you purchase field- and fabric container-grown trees, choose those that have been dug at least several weeks earlier to ensure that the tree will survive the shock from digging. One way to check for this is to see if there are roots growing through the burlap on the outside of the root ball. If you see roots through the burlap, you can be sure that the tree was dug several weeks ago. Until they are established in the landscape, trees harvested from fabric containers will require more frequent irrigation than those from a field nursery (Harris and Gilman 1993).

2) Container grown vs. field grown: A container root ball can have the same or many times more fine roots than that of a similarly-sized tree harvested from a tree being picked upfabric container or B&B from a field (Gilman and Beeson 1996; Harris and Gilman 1991). These roots dry the container media quickly and make most trees produced in containers very sensitive to drought injury after planting unless regular irrigation is provided. They are more sensitive to lack of water after planting than hardened-off field-grown or bare-root trees which have only a fraction of the fine roots compared to containers (Harris and Gilman 1993; Gilman 2001; Gilman et al 1998; Marler and Davies 1987; Gilman et al 2010). Hardened-off field grown trees are better able to tolerate infrequent irrigation because roots regenerate and grow quickly into the landscape soil. Root regeneration from containers is slower, especially when the landscape and root ball stay fairly dry after planting.

Despite differences in root growth and establishment rates (containers take longer to establish, Beeson and Gilman 1992a, Dana and Blessing 1994) after transplanting, shoot and trunk growth on container-grown trees appear to be similar to that on hardened-off field-grown trees provided irrigation is supplied until trees are established (Gilman 2001). However, trees planted from containers appear to be more susceptible to desiccation and death, and they grow slower if the root ball is not kept moist during the early establishment period. For example, citrus trees from containers grew less than bare-root trees in a sandy soil (Marler and Davies 1987). In contrast, recently dug trees that have not been "hardened-off" from a field or fabric-container nursery are more susceptible to desiccation than trees from plastic containers (Beeson and Gilman 1992; Gilman and Beeson 1996; Harris and Gilman 1993). Because freshly dug trees require careful irrigation management, they should not be planted into the southern landscape unless frequent irrigation can be provided. Nurseries are better equipped to handle the special irrigation needs immediately after digging.

Trees planted from containers were found to be less stable (less well anchored) three years after planting than trees transplanted from a field nursery. (Gilman and Masters 2010). This could have implications for stability in storms. Watch videos showing anchorage in 90 mph winds of both 3 years after planting.

3) Container types: There are many container types on the market designed to reduce root circling. Many of them reduce the amount of roots circling the container (Marshall and Gilman 1998; Gilman et al. 2010). Container types appear to have little impact on post-transplant survival and growth. In a recent study, Live oak trees grown in containers treated with copper on the inside surface were more stressed than those grown in conventional containers in the first three weeks after planting to the landscape without irrigation. However, with daily irrigation there was no difference in stress levels. Increased water stress may be due to the lack of roots on the outside of root balls planted from copper-coated containers (Arnold and Struve 1993; Gilman and Beeson 1994). Those from conventional containers have roots on the outer edge of the root ball providing intimate contact with moist landscape soil. This may provide for more water uptake than trees from copper-coated containers. When regular irrigation was discontinued four to six weeks after planting, stress levels were about equal and root growth into landscape soil was similar for trees planted from both types of containers.

Further study showed that Scarlet and Red Oak grown in copper-coated containers had greater regrowth after planting to the landscape than trees grown in conventional containers (Struve 1993). The central leader was left intact and did not die-back as often in trees from copper-coated containers. However, there was no difference in regrowth between container types for Red Maple or Sweetgum. Trees from all container types survived equally well. One advantage of planting from copper-coated containers is that root balls have few, if any, circling roots, making them superior to trees grown in conventional, smooth-sided containers. Shaving the root ball at each shift from one container to the next, and shaving when planting into field soil or into the landscape, results in a better root system with an abundance of straight roots.

Further study indicated that red maple planted from seven different container types responded about equally well following transplanting to the landscape (Marshall and Gilman 1998; Gilman et al. 2002. Live oak from low profile root balls survived poorly after transplanting compared to other container types if irrigation was not provided regularly (Gilman 2001). Survival was similar among container types if irrigation was provided at regular intervals twice each week in the growing season after planting.

4) Collected vs. field grown nursery trees: Native trees, especially oaks, are collected from natural stands and transplanted to landscape sites in certain regions. If held in a nursery for two years after digging, the nursery industry considers the collected trees to be nursery grown (American National Standards Institute, 1996). Research on Laurel Oak indicates that root balls on collected trees are similar to those on nursery-grown trees that are not root pruned prior to transplanting (Gilman, et at. 1992). The only real difference is that collected trees had slightly less fine root mass than trees grown in the nursery. In addition, they often have a thinner canopy until they become established. Collected trees survive but grow slower after transplanting than trees from other production systems (Gilman et al. 1992). No research has been conducted on other tree species or in other parts of the country.

5) Bare root vs. B&B: Hensley (1994) and Bassuk (2000) found no difference between survival and growth of bare root vs. balled and burlapped trees. More recent studies by Harris (2005) and Smiley (2005) in the southern US found similar results. Bare root trees appear to do best when roots are dipped in an absorbant gel prior to planting (Bassuk; Fraedrick).