A quick guide to fruit tree rootstocks

Rootstocks and their effects on tree size.

Apple rootstocks

Nearly all commercial apple trees are grafted or budded onto rootstocks, which determine the size of the eventual tree. Knowing which rootstock is needed, and matching it to the soil and the size you want, enable a tree to be productive and healthy.

Most of the important rootstocks for apples were derived from material collected by East Malling Research Station, UK, in the early 1900s. Researchers collected and characterised the stocks developed by growers during the preceding centuries in Europe. Each one was given a number, preceded by M.

In 1917 The Malling Research Station joined forces with the John Innes Institute at Merton to breed some aphid-resistant rootstocks: the MM101-115 series.

A later development has been the cleaning up of some of these stocks (in conjunction with the Long Ashton research station) to produce virus-free stocks. These are prefixed by the letters EMLA (East Malling – Long Ashton).

In the notes below, M denotes a Malling rootstock, MM denotes a Malling-Merton hybrid.

M27 – Very small indeed, around half the size of M9. Tree needs full support. Fruit size reduced slightly. Moribund in wet soils. Very little pruning is required once the tree is full size (around 5ft/1.5m high; producing perhaps 20 apples a year). It’s OK in pots.

M9 – The best known dwarfing rootstock. It is a cross between a French tree, “Jaune de Metz”, and the “Paradise” apple of ancient Persia. It is known as the “Paradise” stock of Europe. It fruits when very young, is fairly hardy, tolerant of wet but not drought, and compatible with all apple scions. It has to be staked strongly, its roots are slightly brittle, and it is about 8-9ft/2.4-2.7m tall at maturity on an ideal soil.

M26 – A cross of M9 and M16. Used in irrigated orchards on well-drained solis. Fruits early in its life, needs permanent staking, hardy. Susceptible to crown rot and fireblight. M26 is not so good in wet, clay soils where it is rather moribund. Produces burr knots – the beginnings of little aerial roots – which attract pests and which can compromise the tree. These can be sliced off carefully in the garden situation. Planting deeper (so less rootstock is exposed) helps solve the problem commercially. Reaches about 8-10ft/2.4-3m if unpruned. OK in pots.

MM106 – A hydbid of Northern Spy (English dessert apple) and English Broadleaf. Well anchored, fruits early in its life, few suckers, fruit matures late, trees have a long season, OK in pots with less vigorous varieties. Susceptible to crown and root rot. Recommended as a substitute for M26 in wet, cold soil as a little more vigorous. Semidwarf. 9-11ft/2.7-3.3m high. Resistant to woolly aphid.

MM111 – Northern Spy hybrid. About 75% of full size; too large for small gardens. Prone to burr knots. 10-12ft/3-3.6m. Semi-dwarfing or half-standard. Resistant to woolly aphid.

M2 – Very similar in size and vigour to MM111. Not quite so vigorous as M25.

M25 – Full size tree; avoid unless you have a large space in which to grow it. Very vigorous; typically 12-15ft high; can be bigger depending on variety; large, heavy, spreading tree.

SEEDLING TREES – OWN ROOTS

Trees grown from pips are usually M111 size or larger and extremely hardy. Some decorative crabs on their own roots are about the size of MM106 but others (especially native English green-fruited crabs) are enormous.

Cherry rootstocks

Colt – Semi vigorous – 13-16ft/4-5m. Fully compatible with all varieties, Considered very productive until the arrival of Gisela; still good for bush and half-standard cherries on thin soils.

Gisela 5. – Dwarf, 40% of height of Colt. Ideal for commercial orchards, gardens and patio pots.The best garden choice for Cherry Trees.

Pear rootstocks

Compatibility – it should be noted that there are many incompatible varieties when grafted onto Quince (especially Quince C). In these instances a suitable interstock should be used such as Beurre Hardy or Doyenne du Comice. The latter will also impart some resistance to Fireblight.

Pyrus communis (Seedling pear) – Very vigorous. More suitable for half standard and especially standard trees.

Quince ‘A’ – Semi Dwarf. The ideal rootstock for bush trees.

Quince ‘C’ – Dwarf and slightly earlier into cropping.

Pyrodwarf – Limited availability as yet  but this one is proving more compatible with Perry pears and others

Rootstocks for Plums, Gages, Damsons & Mirabelles

Brompton – Vigorous, very suitable for standards, does not sucker and fully compatible with all varieties unlike its predecessors such as Myrobalan.

St. Julien ‘A’ – Semi vigorous. This is fully compatible with all plums, damsons, gages, peaches, nectarines and apricots and many ornamental prunus species. Good yield influence. Not suitable for poorly drained soils.

Pixy – Dwarf and ideal for size containment in the garden. On very strong soils it still has commercial use for strong growing, shy cropping varieties such as Marjories, Avalon and Excalibur. Not recommended for Victoria.

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Grafting Fruit Trees-whip & tongue.

Grafting a fruit tree is not a difficult task, all you need is a firm steady hand,and a good sharp knife. Rootstocks are available for most types of tree. Scion wood can come from any tree of the same type as the rootstock. (usually !)
The general principle is to make a joint between the scion and rootstock that allows sap to flow between the two ,forming a union that will support both for their lifetime.
In practice good carpentry skills work better than green fingers, cleanliness is essential.
The picture below shows the items required, note; the knife has only one bevelled side. I have video footage of the process but it does not show the detail a macro lens can.

The ‘scion’ is a ripe piece of wood taken from last years growth, usually found in the top of the tree. It needs to be firm with little or no pith.
A cut needs to be made cleanly through the scion at a long angle to create an open face 30-40mm long (1.1/4 inch).
In this face make a second cut approximately 1/3 rd down and 6mm into the wood. At all times use a slicing motion, make the knife do the work, if you push it, that is where the damage will occur to your finger! The scion can then be trimmed to length – keeping approx 3 buds.
At all times make sure the cuts are flat and straight as this is the start of the bond between the scion and rootstock,gaps will not callous (or heal ) and the tree will fail.


In the above picture of the scion face you can clearly see the pale or white ring just inside the green ring of the bark, this is the cambium layer which you have to line up with the same in the rootstock.

The cut face to the rootstock is created in exactly the same way – but it is made very slightly larger than that of the scion, you need to be able to see an edge, or line, around the scion, this is to allow the ‘callous’ to form over the wound -reaching the scion, which it joins to, without this edge the callous will grow under the scion and throw it off.

Rootstock showing the ‘tongue’

Now that you have the two ‘halves’ of the new tree it is time to join them together, place the scion-face to face-with the rootstock and lever it up slightly, whilst keeping contact pressure on both, this will open up the tongue on the weaker scion allowing you to push the two together and slide them down into position.

Above you can see the thin line around the scion, this is an essential requirement for the union.

One other factor is to make sure there is a ‘church window’ on the back of the graft-see picture- this will give long term stability to the graft as it heals.

All that is left is to tie the scion to the rootstock, we use degradable rubber strips which fall off after 6 months or so. Other possibilities are polythene strips or self sticking tape. A tight joint is needed to hold the scion in place for 6-8 weeks. Waxing the whole with hot melted paraffin wax is our normal procedure to seal it all in, if you do not have this available then use vaseline on the cut surfaces.
Callous will form quite quickly above 10c-15c. and a union should be formed within 4-6 weeks. Leave the tie / rubber in place until late summer unless it restricts the stem.
Protect the graft with a bamboo cane also to prevent accidental breakage.

This last picture show a graft one year later. the joint can still be clearly seen but has healed well,it will become invisible (mostly) after a few years.

I will add the video to this post later this week but I’m not sure if it will help !
Please – if the above descriptions do not work for you – let me know so I can adjust / re write to clarify.