Peffley: Graft saves trees with serious bark damage

An inarching graft on a mature apple tree. The rootstock, prepared by making a sloping cut to expose underlying tissue, is inserted under an incision made into the healthy tissue of the scion’s bark. The bark is lifted and the rootstock slipped under the flap. The graft will be covered and sealed with wax to prevent drying of the tissues. (Provided by Ellen Peffley)

If you have a valuable tree with serious bark damage and are considering removing it, there is a way the tree might be saved — and this is the time of year to do it.

 

We have an “Arkansas Black” apple tree that produces dark magenta, almost black apples that make the absolute best pink applesauce. Over the years this prized tree has suffered severe damage from repeated cycles of sun and freezes resulting in loss of bark that reaches 6 feet into the canopy of the tree.

Limbs of the tree on the side of the damaged bark have died because the loss of bark disconnected transport of nutrients and water from leaves down to the roots and roots up to the leaves. With the loss of its conducting system and nutrient source, the root system declined with subsequent death of tree limbs.

A drastic method is required to save such a damaged tree — the method is repair grafting. Grafting is a horticultural technique that combines two distinct plant parts: a scion (sigh-on), the top portion, and a rootstock, the bottom portion. Purposes of grafting include changing growth habit of the scion, providing roots with genetic resistance to soil-borne pests or repairing damaged trunks.

It is the latter we discuss today, the form of repair grafting known as inarching.

Elements for successful grafts:

• Tissues of scion and rootstock must be compatible, such as apple to apple or peach to peach.

• The layer of tissue directly under the epidermal layer of bark is the cambium. The cambium of scion and rootstock must touch to allow comingling of cells and regeneration of a healthy union with an intact vascular (transport) system.

• Tissues at peak physiological stage, where the bark of the scion “slips” and can be easily lifted from the outer bark.

Inarching bypasses damaged bark and reestablishes the vascular system from the top of the tree to the roots. The technique uses scions and rootstocks that are on their own roots when the graft is made.

Apples frequently send up suckers, vigorous upright shoots originating from the root system of a tree that are generally undesirable. But inarching takes advantage of the fortuitous production of suckers, as the suckers will be used as rootstocks to bridge the damaged trunk of the “Arkansas Black,” replenishing the declining root system with their own roots.

The goal of grafting is to join cambial tissues of the scion and the rootstock to form a union, allowing for reestablishment of an intact vascular system.

The graft is made by quickly preparing the rootstock (which in inarching is the sucker) by making a long, smooth, slanting cut about 1 inch on its end. Do not allow the surface to dry. Make an incision into healthy scion tissue above the damage. Lift the bark and place the cut end of the rootstock under the flap, joining exposed tissues. Seal the wound with wax; for protection, wrap with tape making certain the graft has been covered.

Make as many grafts as necessary and as you have supply of suckers. Our tree now has eight inarching grafts.

ELLEN PEFFLEY taught horticulture at the college level for 28 years, 25 of those at Texas Tech, during which time she developed two onion varieties. She is now the sole proprietor of From the Garden, a market garden farmette. You can email her at gardens@suddenlink.net.

 

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