Notes on Rootstocks and Scions

  

Apple Tree Rootstocks

In order to create a copy of a given variety a cutting or bud from one year old wood is generally grafted on to a rootstock. In days gone by the rootstocks would have been Malus sylvestris or Crab Apple although today there is an industry developing new rootstock forms that are appropriate for a full range of circumstances.  At its most basic a rootstock will determine the eventual height of the tree. 

Apple Tree Cuttings (Scions)

While it is possible to grow an apple tree from a pip the chances of it producing good quality fruit are not great. Of course commercial breeders do cross pollinate given varieties and thereafter they trial thousands of seeds in the hope of finding the next new thing. Generally, however, the varieties on offer are clones or copies of an original. A present day Cox's Orange Pippin is an exact copy of the original Cox that was raised in 1825.

  

One year old wood of a specific variety is used to graft onto a rootstock. This graftwood is known as a scion and contains the genetic material of the required variety. Scions are harvested when the mother tree is dormant.  A scion from last year's growth contains vegetative buds that will later form leaves and new shoots. 

According to advice from Brogdale grafting is best done about a week after the scion is cut. For our part we think as little delay as possible is best even though folk will tell you the material can be stored successfully in the fridge. This is true to a point - you must double bag and avoid excess moisture in the bag - there is no need to drown them.

Before your start consider how you will label each graft. It is essential to be organised because you must not get the variety name wrong. Be mindful that sunlight turns some ink into invisible ink and similarly sunlight will generally make plastic markers brittle after a year or so. Whatever you do don't attach cable ties to the plant - you'll forget they're there.

As you start a good tip is to pop the scion stick in a little water overnight before starting. Decide if you are going to graft two buds or one - if you do it well one bud per scion will be enough. Of course there are many different grafting techniques although the most important truth is that much of the cambium of the scion should meet the cambium of the rootstock - that is that the two cut sections should match and align. Do not get absorbed by the grafting police who insist on a locking tongue - just focus on aligning the cambiums.

A grafting knife is better than a ordinary knife because the blade is ground only on one face. This allows the blade to be drawn towards the user in one motion. 

With the scion stick in hand cut your first inclined graft angle. Then use secateurs to cut an oblique a cut above the bud you want with the angle shaping away from the bud. Repeat. Then set out your scions (they'll be abour 7cm long) in girth size order. Match their girths to your rootstock.  However it is often impossible to match the scion girth to that of the rootstock so if you can't get an exact match one possibility is to graft on the side. This is an easy and effective method. 

Before you start bear a thought for the grafted bud. Position the bud in a way to give it the best chanceto grow vertically.

First cut the inclined angle on the scion on the same side as the bud you want to use.  This is important because in doing so the bud will grow straighter. Rotate and examine the rootstock. You are searching for an uncurved flat section between nodes. With secateurs cut the rootstock with an angled cut. Now with your knife cut the grafting angle. Use your woodworking skills to fashion a matching space on the side of the rootstock. 

Bind the two sections together firmly - we prefer to use breatheable Buddy Tape from Japan-concept.co.uk although other methods are available. Wax the end with beeswax (electric melting pots are ideal) so the scion doesn't dehydrate and pot this up and keep moist not damp. Make sure the grafted stock is labelled. The grafted rootstock will then callus together - the optimum temperature is 20c. Grafted material held below this temperature will bond OK it just takes longer. 

You are a hero in my eyes if you create new trees!

The buds will burst after a couple of weeks. They will do that without callusing so don't celebrate just yet. Rub off any shoots from the rootstock. Move into a sheltered place when you detect growth. Wind, frost, lack of moisture and insects are the things that will ruin the task. If flowers appear, cut off each inividual floret - they use up energy. In the midst of the flowers you'll eventually find a single leaf growth - that's the one you want to develop.