Interstem Grafted Apple Tree Update, Year Four

UPDATE: See my video series on Inter-stem grafting apples here!

THIS BLOG IS RETIRED, I’VE MOVED TO SKILLCULT.COM   

ALL THE OLD TURKEYSONG POSTS ARE THERE AND MORE, CHECK IT OUT!

It’s been 4 years since I grafted my first interstem apples.  They were in the nursery for a year, and have been in the ground in permanent locations for 3 years.  This is an update on my experience and thoughts so far.  (Read the original post here)

 

A couple paragraphs for those who aren’t familiar with interstem trees: An interstem (a.k.a. double worked, archaic) tree is one that has an extra stem grafted between the rootstock and the upper portion of the tree.  Sometimes the interstem (the stem between the roots and the tree) is there for the sake of compatibility and can be used when the fruit variety is not genetically compatible with the rootstock, but the interstem is compatible with both the top and the rootstock…. think of a kidney transplant, the donor and recipient have to be compatible or the graft will be rejected. Often though, and in my case, the technique is used to dwarf a tree. One problem with dwarf rootstocks is that they are weak.  Sure they are small, which is what we want, but so are the roots.  Interstem grafting allows us to select a large vigorous rootstock, that would normally grow a large vigorous tree, for the roots and a weak interstem to dwarf the tree… small tree big roots.  That means, no staking of the tree, which would be required for a weak dwarfing stock.  They also need less water.

Interstem dwarfs on the left at 8 foot spacing, and oblique (diagonal) cordon row on the right, tresllised, 18 inch spacing about 7 feet tall.  Both will outperform standard trees in production per unit of land.  The oblique cordon are on bud 9 however, and require more water than the interstem trees which have a base of possibly the most drought tolerant of the common apple stocks, M111 and interstem of bud 9.  The largest looking tree there on the left has a short interstem, and is also growing near a waterline leak.

Drought Tolerance:  My primary motivation for grafting interstem trees has been drought tolerance combined with dwarfing, a pairing which I don’t know of any other means of attaining.  I’ve had a few of the trees get a little crispy in the end of summer, but over all, I think they are performing much better as m111 / bud 9 interstems than they would on any stand alone dwarfing stock.  I do water them occasionally, but not a lot.  I probably should ideally water a little more, but I want them to grow up tough and self sufficient, not expecting a drink whenever they want one… tough love.  There is a second row of interstem trees that I will probably move, or just remove, which are not cared for nearly as well as the main row along the driveway.  Most of these outliers have survived and, although they are not doing great, I doubt many would have survived the droughty conditions they are growing in if they were on a straight dwarfing stock like MM109 or bud 9.  I probably won’t water any of the interstems this season since my spring is lower than it’s ever been at this time.