What are Rootstocks?

Rootstocks are trees bred specifically for the performance of their roots.  The foliage and fruit of the tree are inconsequential as the top part of the tree is cut off and discarded.

Different rootstocks are bred for specific purposes, such as the size of the tree, disease resistance, cold hardiness, etc.  Because of the widespread cultivation of apples, more rootstock varieties are available for apples than all other tree fruits combined.  We now recommend using a rootstock called M111 for all applications is hot climates, and here's a detailed explanation of why that you can download.

 

We used to offer more dwarfing rootstocks such as Bud. 9 and M7, but now we will exclusively graft M111 rootstocks on our benchgrafts.

We've found that a warm climate has a dwarfing effect on apple trees and M111  can be easily kept small enough to espalier or pick from without a ladder.  The smaller rootstocks like Bud. 9 also seem to be too wussy for our climate, easily killed by borers and not recovering from damage very quickly.  An irrigation failure can also mean certain death for them.

On the other hand, more vigorous rootstocks like M111 and above are well-anchored and need no staking.  They grow quickly and recover well from damage.  If you forget to water a week they will take it in stride.  They may bear fruit about the same time you allow your smaller rootstocks to start fruiting.  Seedling and M111 rootstocks are long-lived; 100 years or more is quite common.  And with summer pruning, you can keep them any size, even the same size as the most dwarfing rootstocks.

Apple rootstock research is geared toward cold climates.  We have started the import quarantine process for Hashabi apple rootstocks from Israel that have proven there to be more productive in a hot climate.  They should be available in 2014 (sorry, nothing happens fast in the apple world).

A seedling (rootstock planted from a seed) tree like the one above is considered 100% size and can get 30' wide and 25' tall  .  All other dwarfing rootstocks are compared to the seedling for size.  Seedling rootstocks have certain advantages: they are long-lived (this tree is well over 100 years old), their roots go 30' deep and are drought-resistant, they recover quickly from damage, and will bear heavily. 

But they do have some serious drawbacks, such as inconsistency, slow bearing, and susceptibility to wooly aphid, which is the worst weakness.  We think M111 is an excellent compromise between the qualities of dwarfing rootstocks and seedling, and has the best of both worlds.

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