Interstem Grafting of Apples: small trees, big roots

In which I use the tricky manipulation of grafting 3 different apple varieties together to create trees that are small yet drought resistant

UPDATE: to see my new video series on interstem grafting, click here!

Inter-stem trees sprouting on in the nursery row.  Note two bandages on each tree.

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A long time ago fruit tree grafters selected certain rootstocks that would create smaller trees for small gardens and special purposes like espalier training.  Dwarfing rootstocks are naturally small varieties of trees that confer their diminutive size to the fruit varieties grafted onto them.  Early grafters had to make due with a limited selection of these dwarfing stocks, but these days there are ever smaller and more improved dwarfing rootstocks selected for size, rooting characteristics, disease resistance and ability to confer early fruiting to the variety grafted to them.  Some of these modern stocks make trees of only a few feet in height.  Last year I picked apples in a 30 year old orchard that had been grafted onto the dwarfing rootstock Malling 7.  The trees were only about 7 to 8 feet tall making picking and maintenance very easy.  These trees were also heavily loaded with fruit.  One drawback to using dwarfing rootstocks is that they tend to be shorter lived than normal sized fruit trees.  I’m planting trees for posterity and not just for myself, so I usually gravitate toward larger and healthier stocks.  After observing these ease of handling with these small trees and noting that they seemed to be doing well after 30 years I figured maybe there was a place for some dwarfed apples here.

Dwarfed trees may tend to be shorter lived, but they bear at a younger age and can give higher yields per acre when planted at closer spacings.  That’s a nice advantage.  I decided to put in a group of dwarfed trees grafted to varieties suitable for hard cider making.  First I looked for a good dwarfing stock in the 9 to 12 foot high range and decided on the newer Geneva 30 rootstock.  Alas, everyone seemed to be out of it because it was late in the season.  Then I got onto the idea of using an inter-stem.

In inter-stem grafting (also known as double working and interstock) a normal sized vigorous rootstock is used for the roots of the plant, a second variety of dwarfing rootstock is grafted on top of that, and the fruit variety to be grown out is grafted on top of the dwarfing inter-stem.  The result of this strategic placement of genetic materials is a fruit tree of the variety you want, dwarfed by an inter-stem but with a full sized root system to feed it.

!Frankentree!

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Come February and March I rarely step outside without the essential pruning shears stuffed in my back pocket.  The grafting knife gets sharpened and the fridge becomes crowded with scions (cuttings of wood from fruit trees) for grafting projects.  At this time of year, most of my time seems to get used up planting, mulching, caging, pruning fertilizing, training, inspecting and grafting fruit and nut trees.  And then there’s !Frankentree!…

Bear claw scars a few years old add character to !Frankentree!’s pallid whitewashed exterior

The owner planted an arkansas black apple some years back, but the top must have died and only the rootstock survived because the apples were small hard green things not fit for eating.  Not if you’re a spoiled human anyway.  One day I found 4 to 6 inch claw marks covering one side of the tree up to 4 feet and more.  Long curls of bark hung from the scratches.  A few broken branches near the top told the story of a bear climbing the tree to get at the fruit.  When I first saw this tree I was very excited because in spite of receiving no care whatsoever beyond establishment it was putting on good yearly growth and looked healthy and vigorous.  I figured maybe some of the trees I intended to plant in the future might do this well without excessive pampering and was happy.  Since the apples were useless I went straight away to the Scion exchange and collected a large pile of scions to work the tree over to different varieties.  Every year in early to mid march Tamara and I go out to the !Frankentree! to add more varieties.  I graft the scions onto the tree and she makes labels and takes notes to keep track of what we put on and when.  As of today there are 84 distinct varieties (now 140), several unknowns from which the tags were lost or never put on and a few repeats.  The tree had 20 plus varieties of actual fruits on it last year, but the Stellar’s Jays pecked nearly all of them to complete ruins while they were still hard and green.  As soon as acorns were ready enough they abandoned green apple eating and went to work on them.  If the ignorant villagers don’t come after her with pitchforks, axes and chainsaws for being an abomination of nature, I have high hopes for an abundant diversity of apples to taste this summer through winter.

!Frankentree! is an odd spectacle in winter with it’s whitewash, scars, gobs of yellow grafting wax and tags flapping in the breeze. Come summer it looks pretty normal until all the different fruits start sizing up and coloring.

I removed pretty much all the growth from the tree the first year and replaced it with apple varietals.  Some people do this process in stages, but I don’t think it’s necessary if the tree is healthy and vigorous enough and if less crude methods than the usual are used.  The usual top working method, known as topworking, involves loping off limbs 2 to 5 inches in diameter, splitting them open from the end and stuffing in a couple of scions cut to a wedge shape. This method leaves only a few new shoots per tree, and those few shoots have to grow out and gather sunlight for the whole tree.  This method also leaves a large open wound which is not unlikely to become infected.  This chainsaw and axe method of grafting over a whole tree is quick and cost effective, but the small scale orchardist can get fruit much faster and preserve the health of the tree at the same time by making lots of smaller cuts and putting on an equal number of longer scions, a technique known as frameworking.