Another fine tree..

[orangepippin]

Here's one for you FB,

Same variety of apple, one on M9 dwarf, one on M26 semi dwarf
M9 is just lightly summer pruned. M26 winter and summer pruned to keep it in check.

Will both trees have similar yield and size?

Most text books have a diagram showing the progressive increase in tree size on different rootstocks, but in reality it is not that simple, and M9 and M26 are quite close together. The main difference is perhaps the density of the canopy rather than the overall height, with M26 having more branches.

Fruit size is usually noticeably bigger on M9 than M26. Fruit quality can also be better on M9 because its thinner canopy allows more sunlight on to the fruit - although summer pruning will help on the M26.

[FB.]

Fruit quality can also be better on M9 because its thinner canopy allows more sunlight on to the fruit - although summer pruning will help on the M26.

From my perspective, fruit quality is better on M26 than on M9 because of M9's inability to cope with less-than-ideal soils. It's only in good growing conditions that M9 can produce good quality fruit - and not all of us are so fortunate.
For fruit quality in my relatively infertile and relatively dry soil, I would rank:
M25 > MM111 > M26 > M9 > MM106 > M27

In good soil it's:
M9 > MM106 > M27 > M26 > M25 > MM111

[orangepippin]

Fruit quality is obviously affected by soil quality and rootstock, but in the UK, which is at a relatively northerly latitude and experiences cloudy summers, the availability of light is very important.

This is why trained forms like fans or cordons, which have fewer leaves, produce better fruit quality than regular trees. Commercial orchards use tall central leader trees for the same reason, they don't look pretty but a higher proportion of the fruit is outside the canopy.

It's also why late summer pruning - which removes shading from the fruit - is worth considering on trees where the canopy is too dense (which is more likely the case the more vigorous the rootstock).

[FB.]

late summer pruning - which removes shading from the fruit - is worth considering on trees where the canopy is too dense (which is more likely the case the more vigorous the rootstock).

Summer pruning of vigorous new shoots also prevents bitter pit.

M25 actually forms quite an open branch structure (better light availability to leaves and fruit) compared to MM111, MM106 or M116 which all tend to be fairly twiggy/bushy and dense.

Different cultivars also vary in habit of growth and in the amount of bushiness and shading.

Tip-bearers have much less of an issue with canopy shading as a significant amount of fruit is at the outer canopy where there is plenty of light. The downside being the more limited options for pruning tip-bearers to keep them to size while also productive.

[FB.]

Fruit quality is obviously affected by soil quality and rootstock, but in the UK, which is at a relatively northerly latitude and experiences cloudy summers, the availability of light is very important.

This is why trained forms like fans or cordons, which have fewer leaves, produce better fruit quality than regular trees. Commercial orchards use tall central leader trees for the same reason, they don't look pretty but a higher proportion of the fruit is outside the canopy.

Of course, where the soil is of low quality, the vigorous rootstocks end up growing so slowly that they behave like dwarfs - smaller trees with less dense canopies. Even the biggest old Bramleys in this area (50+ years old) are no more than 6m. Apart from Bramley, not many apples trees manage to survive into middle age round here.

As I've mentioned before; for me, M25 and MM111 behave like M26 and M9 do in "the books".
I could grow M25 as a stepover or small cordon in my soil.

[FB.]

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