Wire mesh and biodegradable hessian: why they protect the rootball

Hessian and wire mesh hold together the volume of soil and roots that comes with a field-grown tree. On a large rootball, this containment is needed during lifting, loading, transport and placing in the planting hole.

On rootballs prepared by Diaplant, we do not recommend removing or loosening the mesh during planting. The firming and wrapping were done to work as a single unit. Opening the system up can cause cracks, loss of soil and the break-up of the root mass.

This recommendation applies to the materials and the method the company uses. It should not be extended to trees of unknown origin.

Soil does not have the same cohesion in every field. Texture, moisture and the amount of root all affect its ability to hold its shape.

During lifting, the machine cuts a defined volume. When that volume is raised, its own weight tends to open cracks.

The roots help to bind the mass, but are not enough to guarantee stability in mature trees. External containment preserves the shape until planting.

The hessian sits in contact with the surface of the rootball. It holds back fine particles, reduces erosion and helps to retain moisture.

It is flexible and follows the shape created by the machine and the team. During wrapping, it is fitted without leaving loose folds near the base.

The hessian Diaplant uses comes from specialist suppliers and has biodegradability certification.

The mesh adds strength. It spreads the forces and allows the rootball to be handled without lifting the tree by its trunk.

The mesh needs to be suited to the weight and closed with enough tension to stop it opening. Fitting it should not compress the root collar or cut into tissue.

During transport, the mesh reduces the deformation caused by vibration and changes in support.

To remove the mesh, the rootball has to be disturbed when it is already suspended or sitting in the planting hole.

Opening it can release the firming done in the field. The soil pulls away from the roots, pockets appear and part of the mass may fall away.

On large specimens, the rootball cannot easily be rebuilt once it has lost cohesion. The roots are left exposed, and the tree may lose the capacity for uptake and the stability that justified the transport.

Loosening only the upper part can also start cracks that extend as the ground settles.

How quickly the materials lose strength depends on moisture, temperature, soil and biological activity. The material stays in place for a period and loses strength progressively.

That initial persistence is useful. The roots need time to grow out of the rootball and contribute to anchorage.

The roots grow through and around the mesh. The system should not, however, have rigid wires pressing tight against the trunk or the root collar.

Before backfilling, check the position of the root collar and how the materials finish around the trunk.

Any external tie that could girdle tissue is corrected without dismantling the rootball. The work should be done by someone who knows the system.

The planting level is set by the root collar, not by the top of the hessian.

There are different meshes, wires, synthetic fabrics and methods. A recommendation that suits one rootball may not suit another.

Where the origin is not known, ask the grower for the specification. The project’s specification may also set out its own procedures.

The decision should be made before dispatch. Changing the technique at the moment of unloading leaves the team facing a tree already in the air, with no room to think the solution through.

Some documents require the complete removal of mesh and hessian as a general rule.

Where Diaplant trees are to be supplied, this condition should be discussed at the design coordination stage. The team can present the certificates, explain the method and assess the technical risk.

The aim is not to defend a material for convenience. It is to preserve a root system prepared over years.

The mesh is no substitute for staking or anchoring where these are needed. The tree still needs stability while its roots move into the surrounding soil.

Watering should pass through the hessian and wet the whole rootball. The surface can look moist while the inside stays dry.

The containment material protects the tree in transit. After that, establishment depends on soil, water, depth and aftercare.

• What a tree’s rootball is
• Planting mature trees
• The technical planting sequence

1. Certificates from the suppliers of the hessian and wire mesh used by Diaplant.
2. European Arboricultural Standards. European Tree Planting Standard.
3. Diaplant’s rootballing procedures.