Apple Rootstocks

Apple Rootstocks
M.9 — The most important dwarfing rootstock worldwide, descended from ‘Juane de Metz’ in medieval France, and the famed ‘Paradise’ apple tree of ancient Persia. M.9 is precocious, fairly cold-hardy, tolerant of wet (but not droughty) soils, and compatible with all scion varieties. Increases fruit size, and advances fruit maturity about one week. Its main problems are susceptibility to fireblight, and brittle roots which require a pole or trellis to support the tree. Produces a tree about 25% of full size, usually about 10 feet tall at maturity.
M9(Small)
M9 was the first standardized rootstock available on a large scale, released by East Malling Research Station in the 1920s, with a lineage going back to the ‘Paradise’ rootstocks used for many centuries in Europe.
M9 is probably the most widely-planted of all rootstocks, and the mainstay of commercial apple production. There are a very large number of clones of M9, with varying qualities and vigour. Its only real disadvantage is that it is very susceptible to fireblight, which is endemic to some parts of North America.
Apple trees on M9 are very productive and come into bearing within 2-3 years of planting, the tree reaches full size after about 5 years.
M9 is also an excellent choice for the smaller garden or community orchard.
Mature height: 1.8m – 2.5m
Age starts fruiting: 2 years
Spacing: 2.5m between trees
Staking: Permanent stake required
Good features:
Encourages large fruit size
Resists phytophora (collar-rot and crown-rot) – M9 is by far the most resistant of the Malling and Malling-Merton series rootstocks
Tolerates heavy / wet soils
Problems:
Susceptible to mildew
Slightly susceptible to woolly aphid
Very susceptible to fireblight
Not cold-hardy for northern North American conditions
Can induce brittleness in the scion, so avoid over-cropping at tips of branches.
Suitable forms: Small centre leader / Spindlebush, Small bush tree, Oblique cordon
Requirements:
Watering and feeding required
Ground around the tree should be kept weed-free (e.g. mulched).
M.9/MM.111 Interstem — An interstem tree consists of three parts: the scion variety, the interstem piece, and the understock. M.9/M.M.111 has all the advantages of M.9, but a stronger root system and somewhat better drought tolerance. Should be planted deep, with only the interstem piece showing.
M.26 — A hybrid cross of M.9 and M.16. Very popular in irrigated orchards on well-drained soils. Very precocious, requires tree support, good cold hardiness. Susceptible to crown rot (“wet feet”) and fireblight. About 35% of full size.
M26(Medium)
A popular rootstock suitable for most temperate garden conditions, producing a reasonable sized tree. Developed in the UK where it is regarded as being between M9 and MM106 in vigour, elsewhere its vigour can be quite variable, sometimes being little different to M9.
Mature height: 2.2m – 3m
Age starts fruiting: 3-4 years
Spacing: 3m or more between trees
Staking: Temporary stake for first 4-5 years, or use a permanent stake in lighter soils
Good features:
Reasonably cold-hardy (unlike other Malling-series rootstocks) and fairly tolerant of difficult conditions.
Problems:
Very susceptible to fireblight
Susceptible to collar rot
Susceptible (possibly very susceptible) to woolly aphid
Soils with poor drainage (which facilitate collar rot)
Suitable forms: Bush tree, Small fan or espalier, Large cordon
Requirements:
Ground around the tree should be kept weed-free (e.g. mulched).
M27(Very small)
An excellent rootstock for the enthusiast who wants to plant a lot of apple varieties in a small space – performs very well provided attention is paid to soil and watering.
Mature height: 1.5m – 2m
Age starts fruiting: 2 years
Spacing: 1.2m apart, e.g. 5 trees in 7m
Staking: Permanent stake required
Good features:
Resistant to collar-rot
Problems:
Fruit size can be small – counter by thinning
Very susceptible to fireblight
Susceptible to mildew
Not cold-hardy for northern North American conditions
Suitable forms: Small centre leader, Pyramids, Step-overs, Patio-container tree
Requirements:
Regular irrigation and feeding required
Ground around the tree should be kept weed-free (e.g. mulched).
G65(Very small)
M.7 — Descended from ‘Doucin Reinette’ in France, around 1688. Very popular in areas with cold winters, and deep well-drained soils, like the Lake Champlain region. Suckers profusely, prone to crown gall, resistant to fireblight, tolerates wet soils but does best where it can root deeply. Trees are 50% of full size, or so-called “semidwarfs.”
M7(Medium)
One of the most popular apple of the original Malling-series rootstock in North America because it has good fireblight resistance. Can be treated as a small MM106 in most respects.
Mature height: 2.2m – 3m
Age starts fruiting: 3-4 years
Spacing: 3m or more between trees
Staking: Temporary stake for first 4-5 years, may require permanent stake in lighter soils
Good features:
Resistant to fireblight
Resistant to mildew
Problems:
Susceptible to woolly aphid
Not especially cold-hardy
Suitable forms: Bush tree, Small fan or espalier, Large cordon
Requirements:
Ground around the tree should be kept weed-free (e.g. mulched).
MM102(Medium)
A rootstock from the Malling-Merton series, derived from the Northern Spy apple variety and resistant to woolly aphid. Remains popular in Australia and New Zealand but little-used elsewhere. Producing a tree similar in size to M26.
Mature height: 2.2m – 3m
Age starts fruiting: 3-4 years
Spacing: 3m or more between trees
Staking: Temporary stake for first 4-5 years
Good features:
Resistant to woolly aphid
Suitable forms: Bush tree, Small fan or espalier, Large cordon
Requirements:
Ground around the tree should be kept weed-free (e.g. mulched).
MM.106 — A hybrid of ‘Northern Spy’ and M.1. Precocious, well anchored, does not produce many root suckers. Fruit matures late, and trees grow late into Fall, making them prone to winter injury. Susceptible to crown and root rot. Trees about 50% of full size.
MM106(Large)
One of the most popular apple rootstocks, developed in collaboration by the East Malling and Merton research stations in the early 20th century, and derived from the Northern Spy apple variety (which is resistant to woolly aphid) crossed with the Malling 1 rootstock.
Produces a good sized apple tree for the garden or orchard, which can still be mostly worked from the ground or low platforms. If soil conditions are good it does not require much looking after and tolerates low vegetation around it once established.
Mature height: 2.5m – 4.5m
Age starts fruiting: 3-4 years
Spacing: 3.5m – 4m between trees
Staking: Not essential when planting 1-year trees, otherwise use temporary stake for first few years
Good features:
Resistant to woolly aphid (this was one of the goals of its development)
An excellent rootstock for the backyard gardener, provided the soil conditions are good
Problems:
Not resistant to fireblight
Very susceptible to collar rot / phytophora – best avoided on wet or poorly drained ground
Not cold-hardy
Suitable forms: Large bush tree, Large central leader tree, Large fan or espalier, Half-standard tree
Requirements:
Ground around the tree can be grassed after 4-5 years, keep weed free until then.
MM.111 — ‘Northern Spy’ hybrid. Quite drought tolerant. Not very precocious, minimal suckering, fairly tolerant of wet sites, prone to burr knots. Perhaps best as an M.9/111 interstem rootstock. About 75% of full tree size. A new “G” series of rootstocks developed at Cornell’s Geneva Experiment Station may offer the best traits of the M-series, without the major problems like suckering and disease susceptibility. These are just becoming available from nurseries, and have not been widely tested but are worth a try.
MM111(Very large)
MM111 is an interesting rootstock, little used in the UK where it was developed, because in the relatively benign UK climate its strengths are not an advantage over other alternatives. However elsewhere in the world MM111 is greatly valued for its ability to grow in poor soils. Its only weakness is that it can take many years for the scion variety to come into bearing. MM111 is frequently used as the basis for interstem trees (see above), a role for which it is perfectly suited.
Mature height: 4m – 5m
Age starts fruiting: 4-5 years
Problems:
Can take more than 5 years to come into bearing
Some susceptibility to mildew
Suitable forms: Large bush tree, Large standard tree
Requirements:
Ground around the tree can be grassed after 4-5 years, keep weed free until then.
Widely used in conjunction with M9 or equivalent interstems, which complement it perfectly.
M116(Medium)
M116 is a new rootstock, released in 2002, which can be used as an alternative to MM106. It produces a tree which is about 10% smaller than MM106, but capable of producing the same quantity of apples – making it an excellent choice for small orchards and gardens. It is derived from a cross between the MM106 rootstock pollinated by the M27 rootstock.
Mature height: 2.5m – 3.5m
Age starts fruiting: 3-4 years
Spacing: 3.5m between trees
Staking: Temporary stake for first few years
Good features:
Resistance to collar rot / phytophora (unlike MM106)
Some resistance to woolly aphid (like MM106)
Some resistance to mildew
Some resistance to re-plant disease
Suitable forms: Medium/Large bush tree, Medium/Large central leader tree, Large fan or espalier
Requirements:
Ground around the tree can be grassed after 4-5 years, keep weed free until then.
M25(Very large)
The usual choice for producing a large traditional apple tree in the UK (mainly because it is far more precocious, and slightly larger, than MM111), but little used elsewhere.
Mature height: 5m
Age starts fruiting: 5 years
Spacing: 6m – 7m between trees
Staking: Not required
Good features:
Relatively precocious – unusual for such a vigorous rootstock
Tolerates a wide range of soils, and poor irrigation
Although not particularly disease resistant or resistant to phytophora (collar and crown rot) M25 is so vigorous that it can often outgrow these problems
Problems:
Not cold-hardy
M25 has a reputation for poor anchorage (i.e. it can be blown over) if planted as a 2 or 3 year-old tree and then allowed to crop quickly. For this reason it is far better to plant 1 year-old M25 trees and delay full cropping until year 5. If faced with planting a 2 or 3-year M25 tree, use a large tree stake to fix the roots immobile and leave it for several years until the tree is properly established.
Suitable forms: Large bush tree, Large standard tree
Requirements:
Ground around the tree can be grassed after 4-5 years, keep weed free until then.
G.16 (G.5-A) — Similar to M.9 in tree size and precocity, but more resistant to Phytophthora root rot and fireblight disease. Still requires tree support. G.30-Similar in size to M.7, but more precocious, without the root suckers.
G16(Small)
Another good alternative to M9, developed specifically to be resistant to fireblight, which is endemic in parts of North America. G16 is probably the most fireblight-resistant of all the G-series rootstocks. Grows quite rapidly at first but growth is checked once cropping starts. Produces a tree which is similar to or slightly larger than M9.
Unusually for a tree in this size class, G16 has very good anchorage and may not need a permanent support – although probably best to err on the side of caution.
Mature height: 1.8m – 2.5m
Age starts fruiting: 2-3 years
Spacing: 2.5m between trees
Staking: Permanent stake recommended
Good features:
Very resistant to fireblight
Good resistance to collar rot
Good cold hardiness, but not as cold-hardy as most other G-series rootstocks
A good choice for the home orchardist looking for a small tree
Problems:
Some susceptibility to replant disease
Susceptible to woolly aphid
Can induce brittleness in the scion, so avoid over-cropping at tips of branches.
Suitable forms: Small centre leader / Spindlebush, Small bush tree, Oblique cordon
Requirements:
Watering and feeding required.
Ground around the tree should be kept weed-free (e.g. mulched).
Unusually for a dwarfing rootstock, does not always need a permanent stake
G41(Small)
A new M9-class rootstock derived from M27 and released in 2005. Appears to have all the desirable qualities of M9 but with far better fireblight resistance.
Mature height: 1.8m – 2.5m
Age starts fruiting: 2 years
Spacing: 1m or less between trees
Staking: Permanent stake required
Good features:
Very good resistance to fireblight (similar to G16)
Resistant to crown rot (phytophthora)
One of the most tolerant to re-plant disease
Problems:
Some susceptibility to woolly aphid
Suitable forms: Small centre leader / Spindlebush, Small bush tree
Requirements:
Ground around the tree should be kept weed-free (e.g. mulched).
G65(Very small)
Developed specifically for North American conditions, with good resistance to fireblight and collar-rot. G65 is derived from the M27 rootstock crossed with a Beauty crab apple, and produces a tree the same size or marginally larger than M27.
If allowed to grow as a regular tree, G65 becomes a small shrub-like ornamental crab apple, with pink/white flowers and red fruits.
Mature height: 1.5m – 2m
Age starts fruiting: 2 years
Spacing: 1.2m apart, e.g. 5 trees in 7m
Staking: Permanent stake required
Good features:
Some resistance to collar-rot
Very resistant to fireblight
Cold-hardy
Problems:
Not resistant to woolly aphid
Suitable forms: Small centre leader, Pyramids, Step-overs, Patio-container tree
Requirements:
Regular irrigation and feeding required
Ground around the tree should be kept weed-free (e.g. mulched).
G202(Medium)
Derived from M27, and similar or slightly larger in size to M26. Can be less productive than G11 or M26 in the USA, but better resistance to woolly apple aphid. In other climates it has been slightly more productive than M26.
Mature height: 2.2m – 3m
Age starts fruiting: 3-4 years
Spacing: 3m or more between trees
Staking: Temporary stake for first 4-5 years, or use a permanent stake in lighter soils
Good features:
Good resistance to woolly aphid
Resistance to fireblight
Resistance to collar rot
Suitable forms: Bush tree, Small fan or espalier, Large cordon
Requirements:
Ground around the tree should be kept weed-free (e.g. mulched).
G935(Medium)
Released in 1998 as a semi-dwarf alternative to M26. Produces a tree slightly larger than M26, but significantly more productive. Trees on G935 require permanent support.
Mature height: 2.2m – 3m
Age starts fruiting: 3-4 years
Spacing: 3m or more between trees
Staking: Permanent stake always required
Good features:
Reasonably cold-hardy.
Resistant to fireblight.
Resistant to collar rot.
Problems:
Susceptible to woolly aphid.
Suitable forms: Central leader tree, Small fan or espalier
Requirements:
Ground around the tree should be kept weed-free (e.g. mulched).
Bud 9 — Another useful rootstock is Bud.9, which was developed by the Budagovsky program in Russia. This is a mixed hybrid of Malling clones, crab apples and some traditional Russian varieties. It has all the good traits of M.9, but is sturdier, more winter hardy and less susceptible to fireblight.
Bud.9(Small)
An excellent alternative to M9, with very similar characteristics, perhaps marginally less vigorous. Can ‘runt out’ and stop growing in some situations, but unsurpassed for winter hardiness in this class.
Mature height: 1.8m – 2.5m
Age starts fruiting: 2-3 years
Spacing: 2.5m between trees
Staking: Permanent stake required
Good features:
Resistance to fireblight (much better than M9)
Resists collar-rot
The most cold-hardy M9-class rootstock
Problems:
Sandy soils
Susceptible to mildew
Slightly susceptible to wooly aphid
Suitable forms: Small centre leader / Spindlebush, Small bush tree, Oblique cordon
Requirements:
Watering and feeding required
Ground around the tree should be kept weed-free (e.g. mulched).
P22(Very small)
Used commercially on a small scale, produces an extremely compact tree, the same size or smaller than M27, and with better cold-hardiness.
Mature height: 1.5m – 2m
Age starts fruiting: 2 years
Spacing: 1.2m apart
Staking: Permanent stake required
Good features:
Good cold-hardiness
Some resistance to phytophora (crown / collar rot)
Problems:
Some susceptibility to fireblight
Susceptible to woolly aphid
Some resistance to mildew
Suitable forms: Small centre leader, Pyramid, Step-over, Patio-container tree
Requirements:
Regular irrigation and feeding required
Ground around the tree should be kept weed-free (e.g. mulched).
G11(Small)
Developed as an improved semi-dwarf M26, but turned out to be a true dwarfing rootstock in the M9 class. Good fireblight resistance (like all Geneva-series rootstocks). Increasingly used in US commercial orchards for very high-density (2ft – 3ft) plantings, and generally easier to work with than Bud 9. unless winter hardiness is the outright requirement.
Mature height: 1.8m – 2.5m
Age starts fruiting: 3-4 years
Spacing: 1m or less between trees
Staking: Permanent stake required
Good features:
Resistant to fireblight
Resistant to crown and root rot
Encourages large fruit size
Problems:
Susceptible to replant disease
Suitable forms: Small centre leader / Spindlebush, Small bush tree
Requirements:
Ground around the tree should be kept weed-free (e.g. mulched).