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MOF&G Cover Spring 2011

  

  You are here:  PublicationsMaine Organic Farmer & GardenerSpring 2011Grafting   
 A Spring Grafting Primer Minimize

Whip and tongue graft
A whip and tongue graft works well on small-diameter branches. Make a slanted cut and a tongue in a branch of the rootstock tree. Rob Lemire photo.
A slanted cut and a tongue
Likewise, make a slanted cut and a tongue in the scion. Rob Lemire photo.
Fit the scion into the prepared branch
Fit the scion into the prepared branch. Rob Lemire photo.
Wrap and coat the graft
Wrap the graft completely and coat the end. Rob Lemire photo.

By Roberta R. Bailey

Each of us carries snapshot memories of important and somewhat random events from our lives. In one of my memories, for example, I’m 30 feet up in a tree that I have named the Three Sisters because of its three huge trunks rising from the same spot in the ground. I grafted each of its branches over nine or 10 years, and 18 varieties grow on the tree.

In this memory, I had just climbed about 10 feet higher than my 20-foot extension ladder to finish pruning and grafting one particular section of the tree. I looked down and realized I had climbed onto one of the original grafts. I was stunned that it had grown large enough to support me. That realization and surprise stand as an exclamation point in my life, a measure of passing time and accomplishment.

What Is Grafting and Why Do It?

If you propagate some fruits by seed, i.e., by sexual propagation, they will not produce the same fruit as the parent tree; instead a cross of that parent and the one(s) that pollinated it will grow.

Grafting is a type of asexual plant propagation that preserves the genetic identity of the parent plant. Taking a piece, or scion (pronounced sigh-on), of the parent plant and splicing it onto an existing plant of the same type – for example, grafting one apple variety onto another variety of apple tree – is the only way to replicate the fruit exactly.

Many types of plants can be grafted, including pears, roses, lilacs, tomatoes, potatoes, plums, peaches and apples. With tomatoes, the latest trend is to graft favored varieties onto aggressive rootstocks that thrive in greenhouse environments and impart their disease resistance to the grafted part of the plant above.

Many of the original apple orchards in this country were planted from seed, and most of the resulting fruit was used to make cider. A few trees, however, had quality fruit for eating, and scionwood of these varieties was often shared and named for the farm or county of origin or the flavor of the fruit. If a neighbor has a great apple and you want that fruit on your tree, you must propagate it by grafting.

Grafting your own trees is also economical. A fruit tree from a catalog costs at least $20, while each rootstock (the root and stem onto which the scion is grafted) costs about $2, and scionwood is free or very inexpensive. You can start a 30-tree orchard for about $60 for rootstock and $12 for grafting supplies if you do the grafting and grow the trees for an extra year. If you have existing trees onto which you can graft, adding varieties involves just the cost (if any) of scionwood and grafting supplies.

Rootstock

The more closely related the scion and rootstock are, the more likely they can form a graft, so graft apple wood to apple rootstock or to an apple tree, European plum to European plum rootstock or trees, and pears to pear stock or trees (although pears are sometimes grafted to quince, which serves as a dwarfing rootstock, but quince rootstock is not very hardy and is susceptible to a disease called fire blight). Sometimes, fruits that are not closely related will graft, but these grafts usually do not thrive as they would if grafted onto the same species. I have grafted pear wood onto an apple to hold it until I got some pear rootstock. The pear wood grew for two years but died the third year.

If you have an existing tree, wild or cultivated, you can graft other varieties onto it using a method called top working, which often produces fruit within a few years. The tree already has a considerable trunk and root system, so the graft grows very quickly. You could have a tree with a different variety on every branch.

If you are starting from scratch, you can purchase rootstock from nurseries, such as Fedco Trees. The type of rootstock determines the ultimate size of the tree and is often available in dwarf, semi-dwarf and standard. A dwarf apple tree will often bear within two years but will rarely live beyond 10 years. Dwarf trees require staking, are often not hardy enough for Maine winters, and do not tolerate poorly drained soils.

Semi-dwarf rootstock is somewhat hardier, bears three to four years after grafting, and may produce a tree that lives for 15 or 20 years. These, too, require staking and well-drained mineral-rich soil.

Standard rootstock is very hardy, and, although the resulting grafted trees may take five to 12 years to fruit, they can live for more than 100 years. A standard tree can be pruned aggressively to maintain it as a smaller tree.

Some trees have a dwarfing “interstem” grafted between a hardier rootstock below and the desired variety above.
Bark or rind grafting
Bark or rind grafting uses a scion prepared like one for a whip and tongue graft – but without the tongue. Rob Lemire photo.
Cut into the bark
On a freshly cut branch stub, use the tip of your knife to cut into the bark, parallel to the length of the branch. Sink the tip of the knife into the bark until it stops at hardwood. Sink the rest of the knife edge into the bark with a simple pivot action. Wiggle the knife to loosen the bark. Rob Lemire photo.
Slide the scion into the cut groove
Slide the angle-cut end of the scion into the cut groove until the scion shows only bark all round. Rob Lemire photo.
Three or four scions
A large branch can hold three or four scions. Rob Lemire photo.

Scionwood

You can buy scions from many commercial nurseries or cut them from a tree that you know and love. Members of the Seed Savers Exchange sell scions from many types of fruiting trees, and MOFGA hosts a scionwood exchange annually in Unity (Sunday, March 27, from noon to 4 p.m. this year), where you can donate or take scions of many types of fruit, and attend grafting workshops. (MOFGA holds other grafting workshops as well; see the Calendar in this MOF&G.)

Grafting Tools and Equipment

You will need a sharp knife, grafting tape and a sealant. The knife must be able to hold an extremely sharp edge. A grafting knife is ideal; dozens of models are on the market. If you prefer to dabble and to limit costs, you don’t have to invest much. I have used my pocketknife and a box cutter with great success. The disposable razor edge of a box cutter is always razor sharp.

You may also need hand clippers and a pruning saw.

Grafting tape is a worthwhile investment. I prefer PVC tape, which stretches and has enough strength to cinch a graft closed. It is ideal for top working and for large grafts that may need support for many months. PVC tape must be removed late in the season or early the next year, as it does not break down and could girdle the graft.

You can also secure grafts with rubber or elastic strips or Parafilm tape – a more delicate yet stretchy polyethylene tape that molds nicely to a graft. It breaks down in a month or two, making it ideal for small grafts.

Rubber strips, an older technology, work well in all applications but must be removed manually as they are tight and slow to break down. In a pinch, I have cut wide rubber bands and used them. I have also used hockey tape and masking tape. All work but not as well as a good grafting tape, which is available for $2 to $3 at Agway and some mail-order suppliers such as Fedco.

Any open cuts on a graft must be sealed so that they don’t dry out before the graft union heals and starts to supply the scion with new sap. Traditionally grafters used a soft grafting wax, still available from Agway. I favor Treekote, a quick-drying black emulsion that is easy to apply and is available for less than $10 from Agway and Fedco.

Collecting Scions

Clip scionwood from year-old wood of a tree you want to reproduce. The year-old wood is usually darker and smoother than the older growth. You can tell where last year’s growth began by tracing back from the tip of the branch to the first wrinkled ridge, which can be very slight but is always present. Always cut shoots from a few feet up the trunk or higher, since suckers growing from the ground or base of the tree may have emerged below the graft union and so would not be the same genetically as scionwood taken from the tree above the graft union.

Cut scions while the tree is dormant. If buds on the wood are swelling (“breaking bud”) or showing any green, the graft will not take. In central Maine, I cut scionwood in early to mid-March, before the buds swell, so that it’s stored for less time than if I had cut it earlier. I have cut wood in January and stored it successfully until spring, and I have cut wood right off the tree in April and grafted it that minute – but I had to look hard for buds that were still dormant in April.

Label cut scions immediately and wrap them in a plastic bag so that they will not dry out. Store them in a refrigerator or root cellar, ideally around 35 F – but not with apples. (Apples naturally give off ethylene gas, which can affect scionwood.) I wrap at least three plastic bags around scions to protect them from any gas exposure or desiccation. Some people dip the cut scion ends in wax. This is unnecessary if scions are well wrapped. Long scions can be cut to about 6 inches for more convenient storage.

For the actual graft, a piece of scionwood with only two buds is cut. One bud will do, but two offers insurance.

When to Graft

A successful graft lines up the cambium of the rootstock stem with the cambium of the scion. The cambium is the greenish layer of stem tissue between the outer and inner bark, the layer that will be actively dividing and growing during the growing season.

The ideal time to graft onto, or top work, an established tree is when its sap is flowing, because the graft, with immediate access to flowing sap, begins to form immediately, and the scion has less time to dry out. I try to top work in late April or early May.
Wrap the graft
Wrap the graft. Rob Lemire photo.
Tuck in the end of the wrapping
Tuck in the end of the wrapping and pull it snug. Rob Lemire photo.
Seal the ends of the scions
Seal the ends of the scions and the end of the branch. Rob Lemire photo.
Label the grafted branch
Label the grafted branch. Rob Lemire photo.

Plums can be more difficult to graft but take extremely well if the rootstock is already growing and the sap is flowing when the graft is made. I always graft my plums when the rootstock or tree has just begun to show green in the leaf bud. The scionwood is still dormant.

Graft onto newly purchased rootstock before planting the pencil-thick young tree (unless you opted to plant the rootstock one year and graft it in the ground the next year, or you’re trying again to graft onto a tree on which a graft did not take the previous year). Keep the roots of the unplanted, grafted rootstock moist until you plant the newly grafted tree in a nursery row – in your garden or in a nursery with rich soil where it can grow for a year or two before being dug and established in its permanent home.

Labeling

Always label your trees and make a backup map. Crows and porcupines have stolen my shiny tree markers, and wind has abraded the writing on my labels until they were illegible.

You can make permanent labels by burning or carving plant names into large wooden signs. Then stake the labels at the base of the tree or hang them against the trunk.

Brass engraved labels are also permanent. Recycled slats of window blinds last for years but are not a permanent.

Whip and Tongue Grafting

Grafting is easier done than described. If you can, attend a grafting demonstration or watch a grafting video online. All your doubts will be assuaged.

Of the many types of grafts, I use two 99 percent of the time because they are relatively easy and successful.

For small diameter grafts, such as a bench graft onto a rootstock or a graft onto a pencil-sized branch on a young tree, I use a whip and tongue graft. I cut a piece of scionwood the same size or smaller than the rootstock so that it has two buds. The top cut should be just above the top bud. Do not leave more than 1/8 inch of wood above the bud, as this excess will just die back and need to be removed later. The bottom cut should be 1 or 2 inches below the bottom (second) bud.

Then make a uniform diagonal cut about an inch long on both the bottom of the scion and the top of the rootstock. NEVER touch the cut wood; oils on your hands will contaminate the graft, and it will not bond. The cuts should mate perfectly with each other.

Next cut vertically into the diagonal ends of both the scionwood and the rootstock, starting just above the heartwood, to create a tongue on both pieces of wood. Slide the two together, interlocking the tongues and lining up the cambium layer on one side or, ideally, two sides of the scion and rootstock.

Wrap the entire graft tightly with grafting tape. Start at the top and wrap the loose end of the wrapping over the graft, in overlapping layers, until it’s below the graft. On your final wrap, loosely wrap the tape and tuck its end under the loose loop before pulling it tight.

Seal the open tip of the grafted scion with Treekote or grafting wax or compound.

Label the tree and plant it as soon as possible. If you have to delay planting, store the grafted tree in moist sawdust, hay or shredded newspaper. Before planting, soak the roots in a bucket of water for a few hours.

Bark or Rind Grafting

To graft onto an established tree, study the tree and choose a few branches that you want for its permanent structure. Consider cutting off a few branches that may draw sap away from the branch or branches onto which you intend to graft.

Remove most of the selected branch or branches with a saw or clippers, leaving a stub at least 6 inches long. Sometimes I leave a long branch and graft each of its smaller 2- to 3-inch branch forks.
Young branches (under 5 inches in diameter) toward the top of the tree are good because they are more vigorous. Never graft more than one-third of the entire tree in one year.

To make a bark or rind graft for top working, cut the scion as for a whip and tongue graft but make only the long slanted cut, not the tongue.

Then, on the branch that you cut back to a 6-inch stub, use the tip of your knife to cut into the bark, parallel to the length of the branch. Sink the tip of the knife into the bark until it stops at hardwood. Sink the rest of the knife edge into the bark with a simple pivot action. Wiggle the knife to loosen the bark. If the sap is flowing (as it does sometime in the spring), the bark will lift easily, exposing the cambium layer below the bark and above the hardwood center. If the bark shreds, the temperature may be too cold or the season too early for the sap to flow. Wait until the sap is flowing.

Slide the angle-cut end of the scion into the cut groove. This may be a snug fit. If so, gently tap the scion into the cut until the angle is fully in the base of the branch cut, and the scion shows only bark all round. Place another scion on the opposite side of the branch. I use three or four scions on a large branch.

Wrap the branch with grafting tape, cinching in the scions. Paint the tips of each scion and the open branch with Treekote.

Caring for Grafts

With top worked branches, rub off any shoots that start to grow below the graft throughout the summer and fall. In following years, encourage one graft and prune back the others, eventually cutting off all but the one that grows over the end of the branch.

With bench-grafted stock planted in a nursery area, rub off buds below the graft and prune the top to one branch if it starts to fork. Encourage one tall central leader. Dig and plant the tree in its final location the following spring while the tree is still dormant.

Grafts can grow a few inches to 5 feet in one year. Avoid excess fertilizer, since too much nitrogen late in the season may encourage late growth that does not harden off in time for winter and is liable to die back.

About the author: Roberta writes regularly for The MOF&G. She lives in Vassalboro.


    

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