Rootstock liner help

[happyhermit]

I've just received some semi-dwarf apple rootstocks which I plan to chip bud later this summer or possibly graft next spring. I've potted them up into air pots for the time being as I haven't a nursery bed at the moment.

They are a mixed bunch with quite a range of diameters and not much in the way of roots. Also a lot of them are very curved (I guess from the field conditions). They are also long (18-24") and flop about a bit in the pots which isn't ideal. Should I head them back to straight wood or will this negatively affect root growth? Presumably I need to retain enough of the original stem for budding later this summer? How much?

Would appreciate any advice, thanks.

[FB.]

I find that baby rootstocks are best planted in individual pots of 50/50 soil/compost for their first season, to help them build strength.
'Rose' pots of three or four litre size (about six inches wide and eight inches deep) work well for the first year, then transplant into ten to twelve litre pots (about bucket-sized; 1ft wide and deep).

If you plan to bud-graft in the summer I wouldn't prune the rootstocks; wait until next winter.

My experience is that by the end of the season an piece of rootstock which is neither pruned nor grafted is larger and better established than one which has been pruned or grafted.

[boundtothesoil]

I agree with FB. If you intend to graft them next winter, I wouldn't prune them back now unless they have no roots at all. If you do prune, this year's new growth from the bud immediately below the pruning cut will introduce an unnecessary kink into your main stem, particularly if you are going to graft high. Guide books on grafting tend to advise establishing newly planted rootstocks for a season prior to grafting, inorder to produce a good strong root system. This results in stronger scion growth when you do eventually graft them. Makes sense when you think about it. Given the poor root system on your newly planted root stocks, their immediate priority in terms of partitioning carbon from photosynthesis this year will be root growth rather than shoot/scion growth. That said, I've sometimes been too impatient to wait a year before grafting stocks, and usually get away with it.

[happyhermit]

Thank you both for the replies much appreciated. I've potted them up in 6 litre air pots (the bigggest I could afford!) in a 50:50 mix of soil and JI no.3. Some are ridiculously curved and will spin in the wind damaging the roots. I think I will need to grow on and then perhaps graft next spring. If I graft reasonably high that will give me a second shot in the summer if I have failures.

So, if i trim back to straight wood, should I aim to preserve sufficient (8-12") that i can graft on to this 2yr old wood next spring? Or should I prune low and graft on to the new 1yr old wood in the spring?

Many thanks

[FB.]

If I graft reasonably high that will give me a second shot in the summer if I have failures.

Generally speaking, the higher the graft the more likely the tree growth rate and mature size will be influenced by the rootstock. So if it's a dwarf rootstock, grafting high is more likely to result in extra dwarfing.
High grafts look odd and not very attractive as the tree matures. It's not unusual for the rootstock and scion to be different thicknesses with a bulge where they join.

So, if i trim back to straight wood, should I aim to preserve sufficient (8-12") that i can graft on to this 2yr old wood next spring? Or should I prune low and graft on to the new 1yr old wood in the spring?

I think if you prune low you'll risk snuffing out what little life they have in them. I would leave them unpruned unless there is no other alternative. In a years time there won't be a major issue with failures from grafting scionwood onto a two-year-old rootstock. The problem is when two-year-old scionwood is grafted onto any rootstock; older scions have much lower success rate.

If you must prune them, only remove the smallest amount you can get away with. If they are flapping about in the wind stake them with a bamboo cane or plant them a bit deeper to anchor them better.

[happyhermit]

Understood FB., thanks for the advice. How, high do you generally graft/bud on a semi-dwarf rootstock? Everything I've read suggests 6-8" unless trying to achieve extra dwarfing as you suggest.

[FB.]

Understood FB., thanks for the advice. How, high do you generally graft/bud on a semi-dwarf rootstock? Everything I've read suggests 6-8" unless trying to achieve extra dwarfing as you suggest.

Personally I graft most things as low as possible - about an inch above ground.
My view on that is if the rootstock is not buried the rootstock is exposed to attack from above-ground diseases in addition to the scion, providing two chances for diseases to attack whichever has least resistance.
So you might have a super-canker-resistant scion whose rootstock isn't resistant to (say) canker, with the overall tree resistance being only as good as its weakest link.
Burrknots on the rootstock stem are an easy entry point for canker or crown rot so will expose a young tree to disease until it stops producing those burrknots once it's several years old and the bark has thickened.

With my difficult soil I tend to only use vigorous rootstocks nowadays - MM111 and M25 in the case of apple, Brompton in the case of plum, P.com seedling or Pyrodwarf in the case of pear (there's not much 'dwarf' about Pyrodwarf!).

[happyhermit]

Understood, many thanks.

Is it possible to root any rootstock offcuts? I thought perhaps a bit of hormone rooting powder and pop them in the ground, perhaps in a trench with sand at the bottom? Worth a try even if only a few take.