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Fabric container grown trees
(click on photographs for detail)
Production: Some nurseries produce trees in fabric containers in field soil. Root Control Bags or Smart Pots In Ground are examples of this technology. Applying irrigation and fertilizer only to the top of the root ball will help increase roots in the ball compared to applying it to a larger area around the container (Beeson and Gilman 1995). Many tree species such as pear, maple, ash, holly, crapemyrtle, southern magnolias and others grown in fabric containers are harvested from the ground almost year round and potted into containers or sold directly to the landscape industry.
Root balls of field-grown trees are similar to those grown in fabric containers (See: photo comparison) except that fabric container-grown root balls are less than half the volume (Gilman et al 1992). This makes them easier to handle. About the same percentage of roots are harvested from both non-root pruned field and fabric container root balls (Gilman and Beeson 1996; Harris and Gilman 1991); although other studies show that more roots are harvested in a fabric container than a B&B field grown plant. 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 B&B 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. Nursery operators make provisions for delivering the irrigation needed to prevent desiccation immediately after harvesting. Many trees produced in In-ground fabric containers are potted up into above-ground containers and sold as containerized trees once they have rooting into the media. This makes them easy to handle.
Digging: Trees grown in fabric containers are easier to lift than the same size tree balled-in-burlap because they are smaller. However, they must be handled very carefully. If the tree is harvested early, before the root structure fills the fabric container, there may be little structure or rigidity to the root ball. Roots are easily broken inside the root ball. Fabric container trees also require more frequent irrigation than balled-in-burlap trees until they are established in the landscape (Harris and Gilman, 1993). They require staking to hold them up in the landscape. With these extra precautions, fabric container-grown trees transplant similar totraditional balled-in-burlap trees.
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. However, be sure to purchase trees that have been dug at least several
weeks earlier to ensure that the tree will survive the shock from digging.
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, and others). Trees grown in fabric containers above ground do not have the same limitations.
Handling at the landscape: Root balls of field-grown trees in fabric containers are very fragile and must be handled carefully. Soil inside the ball can become loose from just a moderate disturbance. Never drop the ball because roots will loose contact with soil and trees will shock and are likely to die quickly. Always remove all fabric from the ball before carefully sliding it into the planting hole. Make a slit in the fabric from the bottom of the root ball to the top and gently pull the fabric from the ball. Most people lay the tree on its side to perform this operation. If the tree is held above ground a few days without mulch fabric removal becomes much easier.
Some fabric container designs allow only small-diameter roots to develop outside the fabric; fabric on these trees will be easy to remove without disturbing the root ball. Other fabrics allow large roots to develop through the fabric making fabric removal more challenging. A hand pruner can be used to cut large-diameter roots flush with the inside of the fabric to make removal easier. Some nursery operators use special tools designed to quickly remove fabric from the root ball.
Hardening-off trees: Trees dug several weeks or months prior to shipping to the landscape site are said to be "hardened off". Freshly dug trees are not "hardened off" and are very susceptible to death if not watered appropriately (Gilman 2001). During the "hardening off" period, roots begin to regenerate within the root ball, and the tree may drop some leaves. There may be other physiological adjustments made by the tree that are not now well understood. Some nurseries provide overhead irrigation to the foliage during the hardening off period, especially with summer digging. Purchasing freshly dug trees that are not hardened-off is not recommended.
