Benchgrafts

A benchgraft is an infant tree composed of two parts; a rootstock and a scion.  The rootstock is the roots used for the tree and the scion is a cutting of the variety the tree is to be.  We do this because apples do not reproduce true to seed, and the only way to get an exact copy of a variety is to clone it by grafting.  They are called benchgrafts as the tree is assembled indoors during the dormant season on a grafting bench, as opposed to outside in the field during growing season, which is called "field budding". 

We favor benchgrafts over 2-year-old field-dug nursery trees for several reasons.  First of all is the shipping cost; they are much cheaper to ship as you can fit 200 of them in a 45cm box, whereas 2-year-old nursery trees can only fit 10 or so in a 1.75 meter box.

They also grow vigorously because both the rootstock and scion have been refrigerated, which is important in the tropics as the 2-year-old trees may have trouble with chilling requirements when planted.  It is not uncommon for them to grow 2 meters the first season, making it hard to justify the cost of 2-year-old trees that get their roots damaged while digging them out and branches broken during shipping.

Finally we like them because you are able to train them yourself during the first season, which is important as this will form the basic structure of the tree and set the stage for early bearing.  However, because they are built from dormant rootstocks and dormant scionwood, they are only available certain months of the year, February through early April.

When grafting a benchgraft, we only leave one bud from the scion variety.  We used to leave four or five, reasoning that if one bud didn't take then the others would grow.  In reality either they all take or none of them take, so we went back to one bud.  This also leaves the scion shorter, making it less likely to be knocked out of position during shipping and planting, and it also makes it easier to identify what sprouts are coming from the rootstock below the graft (which should be removed), and which is coming from the scion itself (which needs to be trained up a stick to form the new tree).

Preventing Root Rot

Next to termites, the number one killer of newly-planted benchgrafts is root rot.  The benchgrafts are dormant with no leaves when planted; with no leaves there is no transpiration going on where the roots take up water and evaporate it out of the leaves, so the roots will just sit in any water that's around them.  If they sit too long in the water, oxygen is cut off and  rot will set in, and the scion may sprout for a little bit and then die a couple weeks later.  People see this and assume that it's not getting enough water, and really pour the water on, finishing off whatever life is left.  If you pull the dead tree out of the mud later, you will see the bark is brown and rotting and the roots decomposing.

To prevent this the benchgraft should be watered in once during planting and then not again until it starts to push some leaves.  If the benchgrafts arrive during heavy rains, you may want to start them above ground in a nursery where they can drain well, and then transfer them to the field after they have some leaves and their water needs increase.     

Benchgraft Planting Instructions

Dig a large hole, about one meter across and at least a 30 cm deep, breaking up the soil.  Digging a large, wide hole is the best thing you can do to give your young tree a good start, as you are loosening the dirt so the roots can easily penetrate and thrive.  If you do now know your soil chemistry, consider having it tested so that you can add the necessary soil amendments.  If your tree is on M111 rootstock, plant the benchgraft deep so that the M111 rootstock does not form aerial burr knots (where roots try to form on the trunk above ground, resulting in knobby “galls”).  The graft union should be within two fingers of the ground; on seedling rootstocks you can have it a bit higher or lower with no danger.

Do not mix any manure into the planting hold dirt; doing so will void your warranty.  Moderate amounts of well-aged compost is OK, but it does best sitting on top of the planting hole rather than mixed in, especially if you have heavy clay as it will just act as a “bucket” and prevent drainage.

Form a dish around the tree so it will hold water, and fill up the dish.  Allow the water to soak in, and then fill it again.  This is all the water it should have until it starts pushing leaves, or it will rot the trunk.  After the tree starts to push some leaves, mulch around the base of the tree with grass or leaves.  This mulch will decompose over time, and the tree will send feeder roots up into it to feed, which takes care of most of the fertilizing needs.  Keep the mulch back from the trunk a bit to avoid collar rot. 

Once it sprouts, let the scion bud grow straight up.  If it flowers, carefully pick the flowers off as it is too young to fruit. Rub off any growth from the rootstock below the graft union; if this is allowed to pass the scion sprout, the scion will “runt out” and the rootstock growth will dominate.  Your benchgraft is wrapped with a wax tape; the bud will sprout right through it and there is no need to cut the tape.

You cannot just plant an apple tree in the tropics and expect it to grow by itself into a productive tree; you must carefully train it and the first year is the most important.  We have written a book called Growing Apples in the Tropics that details these instructions and has lots of photos of what you should be doing.  You can see it at the Apple Education page.

Photos: Cleft graft showing cambium layer alignment, 400 benchgraft trees being shipped, single bud on cleft graft scion, benchgraft nursery under the coffee and banana trees, planting benchgrafts in Bugesera, Rwanda, watering newly planted benchgraft in Bugesera.

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