Tree Fruit: Horticulture

Potential Apple Rootstocks for Vermont

The information presented here has been gathered from various sources, our UVM NC-140 Rootstock Evaluation plot, and grower comments -M. Elena Garcia Tree Fruit Specialist

Seedling (adapted to various soil conditions)

Strong Points:

• Well anchored
• Hardy
• Tolerant to fireblight
• Very few burrknots
• Large, vigorous tree

Weak points:

• Yield variable
• Variable resistance to crown rot
• Suckering may be a problem

MM.111 (best on well to moderate drained soils)

Strong Points:

• 80 to 85 % of seedling size
• More tolerant of drought than other rootstocks
• Resistant to WAA
• Good anchorage
• Moderately resistant to collar rot
• Hardy
• Spreading and rugged root system - can tolerate wider range of soil conditions

Weak points:

• Large trees perhaps only 10 to 15% smaller than seedling trees
• Later fruiting than MM.106
• Excessive burrknot development
• Doe not tolerate wet soils
• Tree form is more upright

MM.106  (best on well drained deep soils)

Strong Points:

• Induces early bearing - more so than other semi dwarfing stocks.
• Cultivars usually productive on this rootstock
• Above average tolerance to drought and low temperatures
• Good anchorage and favors good framework and central leader development
• Sucker free
• Resistant to WAA
• Hardy very spreading - penetrating root system

Weak points:

• Susceptible to collar rot and tomato ring spot virus
• Sensitive to "wet foot"
• Resumes growth in the early spring and hardens off in late fall
• Excessive vigor particularly on standard type Delicious that do not bear early
• Dwarfing 70  to 85% of seedling tree development - too large

M.7 (best on well to moderate deep drained soils)

Strong Points:

• Some dwarfing - 55 to 75% of seedling tree size
• Commercially acceptable -was considered the standard planting stock
• Early bearing
• Above average resistance to collar rot
• Above average tolerance to droughty soils
• Major tap root with several branch spreading roots
• Hardy, but not as hardy as M.26

Weak points:

• Severe suckering
• Anchorage only fair - not recommended for Delicious and shallow soil plantings
• Susceptible to WAA

G.30 (well adapted to most soils)

Strong Points:

• 60 to 65 % of seedling size
• Early bearing and more productive than M.7a
• Well anchored
• Much less prone to suckering than M.7a
• Resistant to fireblight

Weak points:

• More testing needed
• May be more difficult to obtain. (Available in 1998)
• Susceptible to common latent viruses
• Brittle graft union with some newer cultivars

M.26 (best on well drained, loamy soils)

Strong Points:

• 55 to 65 % of seedling tree size 
• Easy to prune, maintain and harvest
• Early bearing in some orchards
• Very productive if properly spaced and trees vigorous
• Hardiest of M or MM series rootstock
• Little suckering
• Spreading root system

Weak points:

• Susceptible to fire blight, WAA, collar rot and tomato ring spot virus
• Suckers and excessive burrknots
• Trees require support in many orchards
• Variability in tree vigor
• Some cultivars and spur-types on certain soils have displayed weak growth and crop performance, i.e., Cortland, Macspur and Spur Delicious - must plant on only the best well drained soils
• Very sensitive to "wet feet"
• Possibility of incompatibility at graft union with some cultivars, i.e.,Macoun
• Somewhat slow to harden-off

M.9  (best on well drained, loamy soils)

Strong Points:

• 40 to 45 % of seedling tree size
• Early bearing and capable of good yields
• Resistant to collar rot
• Valuable as interstock on interstem trees
• Easy to prune, maintain and harvest
• Well suited for trellising or training to a post
• Small - confining root system

Weak points:

• Trees need support because of brittle root system
• Bark attractive to mice
• Suckers
• Susceptible to fire blight and wooly apple aphids (WAA)

Bud. 9 (does not tolerate wet soils)

Strong Points:

• Promising new rootstock
• 35 to 40 % size of seedling
• Very resistant to collar rot
• Hardier than M.9

Weak points:

• Needs support
• Moderately susceptible to fireblight and tomato ringspot virus
• Drought susceptible

P.2  (best in well drained soils)

Strong Points:

• 35 to 40 % size of seedling
• Very early bearing
• Resistant to crown rot
• Very little suckering

Weak points:

• Needs support
• Moderately susceptible to fireblight
• Susceptible to tomato ringspot virus

M.27 (best on well drained, loamy soils)

Strong Points:

• 25 to 30 % of seedling size, or even smaller
• Very dwarfing (4 to 5 feet ) and somewhat hardy
• Very early bearing
• Resistant to collar rot
• Useful as interstock on interstem trees
• Easy to prune, maintain and harvest
• Smaller - confining root system

Weak points:

• Poor anchorage because of brittle root system - tree needs support
• Susceptible to fire blight
• Only suitable for vigorous growing cultivars
• Easy to 'runt-out'

Ottawa 3 (well drained soils)

Strong Points:

• 50 to 55 % of seedling tree size
• Early bearing
• Very productive
• As hardy as M.26
• Resistant in most soils to crown rot
• Very few burrknots

Weak points:

• May need support
• Roots poorly; may be a factor in orchard establishment
• Moderately susceptible to tomato ringspot virus and common latent viruses

EMLA, 9, 26, 7 etc. (Virus - free)

Strong Points:

• Cultivars on virus-free rootstock are more vigorous than those on virus-infected rootstock
• Virus-free M.9's probably will produce larger yields than virus-infected trees
• Yield efficiency (pounds of fruit/unit of space occupied) may be higher
• Fruit quality may be better because they have stronger growth, may require less "tender loving care"

Interstems (Best on well drained, loamy soils)

M.27M.9/MM 106 (adapted to most soils)

Strong Points:

• 50 to 60  seedling size
• Early bearing
• Productive
• Moderate hardiness
• Easy to prune, maintain and harvest
• Spreading root system

Weak points:

• More expensive than single worked tree
• Usually only available by contracting 2 years in advance of planting
• Lack of data on long-term performance
• On some cultivars and spur-type, it may be difficult to develop a strong central leader
• Suckers from rootstock and interstem piece (especially when stem piece is planted above soil line)
• The interstem piece is generally M.9
• Burrknots* on the M.9 stempiece are common
• Tendency to cause inconsistent tree development and crop performance
• Posting usually required when interstem portion planted above soil line
• Stem piece can often become distorted in form

M.27, M.9/MM.111 (good in most soils)

Strong Points:

• 50 to 60 % of seedling tree size
• Early bearing
• Very productive
• Moderately hardiness

Weak points:

• Similar to the previous combination