Posts tagged #Grafting apples

Interstem Grafting of Apples: small trees, big roots

UPDATE:  See my video series on Interstem grafting apples here!
UPDATE: See my video series on Interstem grafting apples here!

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

Grafted trees sprouting
Grafted trees sprouting

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

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.

The conditions in this area are essentially a wet-ish Mediterranean climate.  We get plenty of rain each year, but it stops completely for the summer months at which time it can be very hot.  Even when it rains in the summer, which is very uncommon, the quantity is never enough to really soak the ground enough to water a tree.  Vigorous healthy drought resistant stocks are best under these conditions.  For the bottom rootstock I chose m111 which is very slightly dwarfing but drought tolerant while also being resistant to heavily waterlogged soils and the pest wooly Aphis.  It is a rootstock long tested by service and the one I have used almost exclusively here so far.  For the inter-stem I used bud 9 which should make a tree averaging in the 8 to 12 foot range.

One of the drawbacks to grafting interstems is that two years are supposed to be required to grow an inter-stem tree, but that turns out to be untrue.  First you are supposed to graft over the interstem onto the lower stock, and the next year you add the fruit variety you want on top of that.  The apple is an easy fruit to graft and with the great success I've had grafting apples in general I decided it would be worth a try to graft all three pieces together the first year.  I did a quick internet search was emboldened by finding that someone else reported doing just that very successfully... that discussion thread is here on the Home Orchard Society site.

One issue with grafting in general is that you are working with a stick that has no connection to the ground at all until the graft heals and therefore no way to replace any water that it uses up in trying to grow or loses to evaporation.  After grafting this stick to the rootstock it slowly begins to form callus tissue which links up with the callus tissue from the healing rootstock to form routes for food and moisture to flow into the scion allowing it to grow on.  The time between making the new graft and the healing and uniting of these tissues between stock and scion is a dangerous one for the scion.  When grafting the interstems and the scions both at once there are two of these unions to heal before the scion receives nutrients and water.   In light of these considerations I used a simple technique that I've been playing with for a few years to protect scions from moisture loss.  That technique is simply to paint the scions, and in this case also the interstems, with grafting "wax" to slow the loss of moisture.  I've used Doc Farwells grafting wax which is essentially a thick yellow paint that remains somewhat flexible.  I try not to paint over the buds or, if so, then lightly.  It seems to work.  I used primarily whip and tongue grafts... a little on that here.  Unless the scion and stock size were very different in which case I used cleft grafts.  I prefer the whip and tongue generally as it is stronger and less liable to break if disturbed.

Healing cleft graft
Healing cleft graft

Out of 23 trees double grafted this year I lost only two, one of which died completely (preventable if I hadn't been pulling off all the suckers as they came out) and one on which the top died, but the bud 9 stem is sprouting and growing up again so I can re-graft it next year.  Both probably failed due to poor scion wood, so if I would have had better scion wood, I think I would likely have gotten 100% take. They're generally growing well too except a couple that, again had really poor scion wood and are having a hard time getting off the ground.... and may not really.   Still, totally acceptable, and improvable, results.

interstems growing in July
interstems growing in July

UPDATE FALL '10.  The interstem trees in the nursery bed are considerable larger than the trees that are on just bud 9 roots.  This would indicate, as I hoped, that the larger root system cancels out some of the dwarfing effect.  That is fine with me since the bud 9 trees would probably be a little smaller than I wanted, and I was actually hoping this would be the case.  I have not looked closely yet to see if there is a correlation between interstem length and dwarness, which some sources say there is.

I had to buy bud 9 rootstocks to get the interstems I needed, and after grafting the bud 9 interstems onto the m111 roots I grafted the left over bud 9 roots to some select dessert varieties and a few more cider varieties that I want to test out.  I'm not sure exactly what I'm doing with the bud 9 trees yet, but I'll probably plant them only a couple feet apart in a long row and train them each to a single stem wired to a trellis and grown only a few feet high.  This arrangement should give me a little laboratory of very early bearing trees to test out interesting varieties.

I saved a few inter-stem stocks for varieties, like Harrison, that I want to grow but was unable to acquire this year.  Once I can test some of these varieties in my climate and see if they suit my cider making tastes, I can rework the trees to other varieties as needed, grafting on whichever ones I find most suitable, or even just testing other new types that I acquire through trading or scion exchanges.  The new inter-stem trees should be ready for the ground this coming winter/spring.


Interstem tree varieties as of 7/10 (this list has greatly changed as of 3/13) King David 2 Wickson 2 Ashmead's Kernel 2 Muscat De Bernay 2 Dabbinet 3 Yarlington Mill 2 Marmora Gold 1 Harry Master's Jersey 2 Court Royal 1 Tale Sweet 2 Kingston Black 1 Stoke Red 1 Somerset Redstreak 1 Ellis' Bitter 1 Muscat De Dieppe 1

EDIT Feb 2013:  These trees have done very well.  The ones that I got into the ground and grew out right away are over head height and some bore fruit last year.  They seem quite vigorous.  A few were grafted over to other varieties which has delayed them.  Many will provide a framework for grafting over to other varieties this year as I've changed my thinking on what I want out of them--- which is more dual purpose and dessert apples and less specifically cider apples.  I may post a follow up at some point (WHICH I HAVE HERE).  I have also done more interstem grafts and they have generally gone very well grafting all three parts at once.  As an experiment, I did an interstem graft, and then stacked another 5 varieties on top of that just to see if they would take.  Although some grew more than others (varietal dependent) all 6 grafts healed and grew!

Read the 4 year update here!


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!...

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.

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.

At first I used a side graft method from the Grafter's Handbook that just didn't work that well.  In this method you cut into the side of a main branch deeply at an angle.  The scion is cut to a wedge shape similar to that used in cleft grafting (see pics below) and then simply stuffed tightly into the cleft which pinches it and holds it in place without any wrapping.  It does have to be covered in grafting wax though.  The success rate on these grafts was probably less than 50% which is very poor for apple, an easy to graft fruit.  I also didn't like the fact that the branches then came out at an angle right along the parent branch instead of growing out and away from it.  that makes a bark inclusion in the tight space between the parent branch and the new scion branch, which arrangement is both weaker and more disease prone.  It is also very hard to line up the cambium layers in this method because the bark on the branch and the bark on the scion are very different thicknesses.  I imagine one could get a better take with practice, but I still don't like the other drawbacks.  The advantage is that you can put a new side branch on wherever you like, which is great when there doesn't happen to be a shoot to graft onto.

Since then I've done almost exclusively whip and tongue or cleft grafts which work great.  I only use the side cut method above when I need a branch where there is no small stub to graft onto.  Now that some of the older grafts are quite large I'm grafting material onto the ends of them to try out new stuff.  If something fruits and I'm not impressed with it, it can be replaced by something new that I'd like to try out.  I have a growing apple wish list large enough to require a couple more !Frankentrees!  When adding scions I get the longest scions I can.  Unfortunately people cut them short to fit into plastic ziploc bags, so they are usually shorter than I would like.  I learned from the grafter's handbook to use long scions with 8 or 9 or more buds when top-working (working over an existing tree to new varieties) because they will fruit faster.  When grafting onto a young roostock you need only two buds and one of them is just for insurance in case the other doesn't grow.  I usually select the stronger of the two and pinch out the other early on.  The rationale for using long scions in top-working is proved out by experience. If there are only a couple/few buds on the scion then they will all go vegetative and grow into long shoots.  If the scion has many buds generally the ones near the tip will grow out into shoots and the shoot can afford to turn the lower buds into fruiting buds.  I've actually gotten fruit the first year when there were already fruiting buds on the scion.  That kind of precocity is unusual, but it's not unusual to get a few fruits the second year and a good little crop the third year.  Early fruiting can also be encouraged by summer pruning.  Pinching back any vegetative shoots that you don't require to grow long will encourage the formation of fruiting buds near the base of the shoot.  Pinch a little off the tip when it has grown out pretty long and then come along once or twice more during the summer and prune it back yet further.  At the end of the season you end up with a shorter shoot with the lower buds differentiating into fruiting buds.  It seems to work pretty well on many varieties and helps to control the more vigorous growing types so that they don't take over the tree.

At some point !Frankentree! will hit some real world limit as to how many varieties you can practically fit on one tree and still expect to get good fruit from them.  I use the tree somewhat for holding wood I might want later and early on I just wanted apples period.  Now I'm more inclined to use it to test varieties I want to try.  Many rare varieties are very difficult to find samples of for taste testing.  Furthermore, even if you can find them there is no guarantee they will be in their best state, in fact, they usually won't be.  some apples are best off the tree.  Others ripen and improve with storage... some with lots of storage time, some with only a little.  Some years they taste better than others.  Besides, I want to know if the apple does well here and actually tastes good when grown in this climate, or stored until March or April or may.  The Earliest apples on !Frankentree! so far are Red Astrachan in mid to late July and the latest is Lady Williams which should hang into February.  The Jays knocked the last Lady Williams off the tree in mid January and it wasn't ripe yet.  So far the most intriguing apples !Frankentree! has bourne have been Karmijn de Sonneville, Cherry Cox (yes, that's an apple not a pornstar) and Egremont Russet.  I think this year is going to be very fruitful for our mutant friend... if the jay problem is resolved.  I'm trying to think of a human comparison to !Frankentree!, but it's not really possible.  Each variety of apple was originally grown from a seed or occasionally, as in Cherry Cox, was a mutated branch of a particular variety of apple known as a sport... in the case of Cherry Cox it was a mutant branch on a Cox's Orange Pippin tree which is widely thought to be the benchmark in flavor for apples.  You might think I only got Cherry Cox for the name, but really that was only 9 /10th's of it.  It has the complex flavor of Cox family apples with a varying degree of cherry essence in there.  I do like saying Cherry Cox though.  Anyway, each variety is genetically different and has been cloned by grafting cuttings over the years... in some cases hundreds of years.  Court Pendu Gris which I grafted today may be go back as far as the 1300's!  So imagine if people had these little stubs that you could graft bits of other people onto and they would grow into arms identical to those peoples arms.  So a person could have like 84 arms... except the fingers have leaves and are holding apples.  Dude, that shit could totally happen!  !Frankentree! indeed.

Operating on !Frankentree!

UPDATE:  During the 2010 season I had about 30 varieties fruit on frankentree.  Some I had already had before and some were new.  A few were eaten by birds.  I have so far usually added about 20 or 30 new varieties per year, so If good blooming weather prevails this spring, hopes are for a large number of new varieties in the 2011 season.  Some varieties like Connell Red (which looks like just regular fireside to me) and red astrachan are getting grafted over because I'm simply too little impressed by them and need the space.  With many new scions acquired through trade this year I need all the room I can get.


UPDATE FEBRUARY 2012:  One of the risks of putting a lot of varieties collected from random sources onto one tree is the risk of disease transmission.  This spring, sadly, Frankentree was infected with the Apple mosaic virus.  It is a common virus in Apples.  Varieties vary in their susceptibility, but all can carry it.  Susceptible varieties will show chlorotic (having a lack of green chlorophyll) spots on the leaves with may become sunburned in the summer.  The virus doesn't kill the plant, but it can make it less healthy and productive.  By the end of the spring a had 140 unique varieties on Frankentree collected over about 6 years.  All of those are now infected with virus.  Most are replaceable, but a couple like rose pippin and Beccas little pink tart might be difficult to replace.  Regardless, I am unable now to use the wood from frankentree as propagation material for my own use and to trade with others.  I can still use him as a testing ground for the varieties that are already on there, as well as for testing new material that I can reacquire if I decide I like it after it fruits.

Varieties which showed the most symptoms are:

Cherry Cox Ribston Pippin Gold Rush Cameo Netto’s Late Tart Hudson’s Golden Gem Sunrise Allington Pippin Karmijn De Sonneville Connel Red Allen’s Everlasting Cox’s Orange Queen Ambrosia Lady Williams

The better news is that we got 30 or more varieties of apples off of him this year.  We're looking forward to trying even more next year.  I will be thinning out a few losers this year as some material that was put on just to hold it over, and maybe adding a few things to test, but mostly I think Frankentree will become less of a test tree now and slowly be shifted over to just the varieties which prove to do well and taste great.

UPDATE 2014:  I get a lot of different apples off Frankentree every year now.  The Mosaic virus has proved to not be much of a problem and doesn't seem to affect yield or much of anything really.  See also my youtube video introducing Frankentree