Turkeysong

Experimental Homestead

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

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.

A healing cleft graft. I only use these when the scion is smaller than the stock as in this picture. Whip and tongue grafts are more stable and seem to do better early in their growth.  The white and beige puffy stuff in the joint is the callous tissue that ultimately joins the two pieces.  this one has just been unwrapped and was immediately painted with grafting wax to protect the soft, tender and tasty tissues from insects and sunburn.

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.

Interstem trees growing on in July. I’m taking good care of them in hopes of getting nice tall maidens to try out a new (old actually) training technique wherein most of the buds are removed leaving only those at the intervals along the stem where branches are desired. Preliminary results this year were good and I’ll probably blog about it next year if it works well on this batch of trees.

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.

CHEERS!

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.  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!

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July 20, 2010 - Posted by | Food and Drink Making, Food Trees Fruits and Nuts | , , , , ,

15 Comments »

  1. Those are very healthy-looking young trees – nice job!

    I did some topworking for the first time this spring, and some of those are now growing out nicely. Need more King David!

    Comment by Tim | July 20, 2010 | Reply

  2. If you need King David wood get it from Tim Bates. He has vigorous healthy wood and leaves them full length, so you can get nice long scions to do the 8 to 10 bud scion method, which I think really makes a difference in earliness of bearing. I’ll pick it up for you if you don’t make it to the exchange, and I’ll have at least a little bit. I was going to do two of these to King David, but ended up with only one:( Your KD Muscat De Bernay cider was inspiring! My M111 KD is just starting to bear. I like calling it KD because I hate biblical names ;) Cheers!

    Comment by turkeysong | July 20, 2010 | Reply

  3. This is an excellent photo essay. You can read more on interstem grafting here:

    http://www.homeorchardsociety.org/forums/viewtopic.php?f=1&t=1198

    Comment by Jade Rubick | August 20, 2010 | Reply

  4. Great interstem grafting info. I’m going to try this in the spring. Did you ‘cure’ the graft before planting it? An old timer suggested that I keep the graft in a cool, dark environment (like a cold cellar) to allow for better healing.
    What do you think? Cheers, Stu

    Comment by Stu Reid | January 2, 2011 | Reply

    • Stu: I never take extra steps to cure any grafts. Perhaps that would increase my success rate with more difficult fruits like peaches and almonds, but I can say that in this climate, barring unusual weather, nothing of that sort is necessary for apples. I’ve accidentally forgotten to wrap apple grafts at all on numerous occasions and just the plain graft in the open air with no wax or sealing tape will often take if the fit is good. I will tend to shade the trees after they are in the ground. I graft inside making sure the roots don’t dry out, soak the roots in water overnight and store in damp sawdust or sand outside until I can get them in the ground preferably within a week or two and not too far before its getting on toward bloom time. I also like to put a dab of grafting wax on the tip of the scion, but in the case of the interstem, or just if I am worried about the graft drying out before the graft takes for some other reason, I’ll paint the scion with grafting wax to slow evaporation… except for the buds which I leave unpainted. I do know people who expose just the grafted area to a heating element to grow a calloused union before planting, but apples are so easy that I don’t see the point. Again though, that is here where the weather is fairly mild for the most part. If your old timer seems like he knows what hes talking about maybe you should give it a shot. As long as the material is well cared for and not allowed to dry out I don’t see that it would be a problem. I don’t know what your grafting experience is, but you should be sure to make tight grafts with flat surfaces. That is important so if you are not up to speed, get your grafting knife shaving sharp (literally) and practice on prunings until you are confident you can make grafts that make excellent contact. Good luck and I hope you will report back next year!

      Comment by turkeysong | January 3, 2011 | Reply

  5. Your experiment is being conducted by me as if we had the same targets.To make an inter-stem in one year I grafted M106 with M9 and Mollies delicious cultivar. The plants have started bearing just in the 2nd year. The inter stem piece was just 6-8inches. I would like to know the length of inter stem piece you have used in your
    experiments.
    with regards
    AR

    Comment by A.R.Wadoo | January 3, 2011 | Reply

    • Yes A.R., I’m sure the question of the feasibility of making double grafts in one year comes up for many people who want to graft their own inter-stems as it did for you and I. I’m glad to hear your trees are doing well and that they are indeed precocious as that is one of the factors that influenced me as well. Mine look great and will be put in permanent locations in February or March. Did you have a high rate of success as far as the rate of take? From my experience I would think that with good technique, stock and scion material and timing the success rate could approach that of single grafts, and certainly good enough for a very acceptable rate of losses. I was at first puzzled why sources claim it takes two years to produce an interstem tree, but then realized that may be simply to conserve material as you can use one interstem bud to produce a tree with budding and it takes a stick with many buds to make it in one year. It also takes more varietal scion wood to do a dormant graft and I get the impression that a lot of nurseries prefer summer budding. Still, it seems like a tree in one year instead of two might offset those concerns.

      I don’t recall the details, and didn’t take notes, but I think I remember reading conflicting views on whether the inter-stem length was a very significant factor in tree vigor. Since I have droughty conditions and I want the trees to be on the large side of the bud 9 range anyway I wasn’t too worried about making short inter-stems so I think I was pretty cavalier regarding stem length. I think I did a couple extra short and some as long as 10 inches just to see what would happen. I believe most are in the 6 to 8 inch range but I really can’t be sure and they are totally random as regards varietal selection. Best wishes for your orchard.

      Comment by turkeysong | January 3, 2011 | Reply

  6. Hey Steve,

    Thanks for the feed back. I can’t remember where I got this from but apparently the interstem length has little effect on the ultimate size of the tree. Unlike a single graft where the higher the graft the stronger the dwarfing effect. Maybe I’ll try a few to see. Boy I hope I get bearing trees in the 2nd yr.

    Nice selection of scion Steve.
    I hope to get Wickson this spring. Here’s where I shop for scion:

    http://www.seedsanctuary.com/fruittrees/index.cfm

    Cheers,

    Stu

    Comment by Stu Reid | January 8, 2011 | Reply

    • I thought I remembered reading some conflicting data on interstem length, but basically decided I probably would rather just see what happened I guess. Wickson is awesome! I’ve never tasted anything like it except maybe crimson gold another etter apple. I’m very curious to try the rest of the Etter crabs offered through greenmantle. I have a special interest in Etter apples because of local history (next county over) and they seem to be unique and quite good as far as I’ve tasted so far. The fact that Etter named Wickson after the famous California agriculture champion tells something of his own esteem for it. I have some Wickson cider aging down under my bed which I’ll be busting out to try soon. Preliminary taste tests were interesting. It doesn’t keep the best (suffers in flavor and texture both) but it sure is good in season. By all accounts around here it is also a healthy grower and productive. You might check out this page if you are in Canada…

      http://www.appleluscious.com/network/scionwood.html

      If you are in the states, I can give you Wickson. Contact me through my website paleotechnics.com

      Comment by turkeysong | January 8, 2011 | Reply

  7. Thanks for the link……I hope to get Wickson from Harry Burton (Apple Luscious). Have ordered scion from Harry before…interesting guy. Made it to the 2010 Salt Spring Island Apple Fest which he helps co-oridinates. They had just under 300 Heritage apples on display of which I tasted approx 100 var.

    Comment by Stu Reid | January 9, 2011 | Reply

  8. Wish I could make it to the apple fest. I never get to taste that many apples at once, but will soon when more of my stuff comes into fruit. I had about 30 this year. Whats hard with those tastings is that you don’t get everything at its best. You almost have to grow your own to be assured you are getting the apple when its best for eating… that is assuming it does well in one’s area, which is not always a safe assumption. Good luck with your projects!

    Comment by turkeysong | January 9, 2011 | Reply

  9. Topworked a few more of my trees with KD, including those loooong scions you gave me. They all took and are growing out from the tips. Will be interesting to compare performance of the long scions with regular-length.

    Topworking is basically a kind of interstem grafting… one thing to watch for is matching the bloom/leaf-out times. I put KD onto Sweet Coppin, which for me is a very late bloomer and doesn’t even leaf out until June, whereas KD is bustin’ out in April (yet is mostly unaffected by the hail and rain). The first year grafts did not leaf out until June/July, and I worried about that, but this year the scions are leafing out a little earlier. I am wondering if the KD will “train” the trunk wood to get going earlier. As you know, the tops communicate with the roots by sending chemical signals down (and vice-versa), so it’s not too far-fetched an idea. I still have a couple of SC so will be able to compare leaf/bloom dates to see if this is happening.

    Fun stuff. How’s your 2010 vintage? I only pressed about 40 gallons, all of it very late (so the apples weren’t in top condition) and it’s not clearing well – except the KD. Haven’t dared taste yet, but I don’t expect stellar results.

    Comment by Tim | June 10, 2011 | Reply

  10. I still haven’t bottled everything from 2010. I hardly got any apples actually. I’m drinking the stuff from the previous year which is mostly not so good. One wild yeast ferment that is interesting, but kind of sweet for my preference. And one that really makes better mimosas that it does a straight drink. I did a few interesting apples in micro batches of like 1/2 gallon that I’m hoping will be tasty. I checked them once when mostly fermented and a couple seemed promising including the King David. The Edwards Winter made a delicious fruity juice with marked astringency. I’m hoping to bottle soon. Maybe I’ll do it tonight and report back. I have a feeling I’ll be frameworking a lot of my trees over someday… probably to King David so you won’t have to say I told you so when it happens :) My 2010 wine is suitable only for sangria, but it does that pretty well! “…a light, dry, young, acidic, unoaked, inexpensive red wine,” yep, thats it.

    Comment by turkeysong | June 11, 2011 | Reply

  11. […] of the inter-stem apples that I planted a couple of years ago were re-grafted to new varieties.  Most are dessert or dual […]

    Pingback by Turkeysong, the Year in Pictures 2013 Late Winter and Spring « Turkeysong | January 8, 2014 | Reply

  12. […] as always, is to learn to graft them yourself. Grafting in one year:  BTW, you can read my previous post on interstems for details, but all of these were grafted in one year, making both grafts at once with dormant […]

    Pingback by Interstem Grafted Apple Tree Update, Year Four « Turkeysong | August 9, 2014 | Reply


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