Stepover Apple Trees: Winter Pruning, Year Three

‘Howgate Wonder’ apples growing on a stepover tree, September 2021

For background info, please see:
Stepover Apple Trees: Winter Pruning, Year One
Stepover Apple Trees: Winter Pruning, Year Two

I’m growing three stepover apple trees on our main allotment plot and, instead of following the standard advice in most of the fruit tree pruning manuals, I’m pruning them in the winter months when they’re dormant, rather than in summer when they’re in full growth.

2022 is the third year of this deliberately unorthodox pruning regime, and I’ve held off on posting this year’s update until blossom season, so that I could show you just how well winter-only pruning seems to be working.

First, a quick re-introduction to the trees. Two of them, it has to be said, are almost entirely unsuitable to be grown as stepover forms. One is a ‘Blenheim Orange’ on MM106 (half-standard, non-dwarfing) rootstock[1]. and the other is a ‘Howgate Wonder’, also on MM106. I planted them before I was properly informed as to quite how vigorous those two varieties are – both triploids, both producers of large, dual-purpose apples – and quite how unsuitable MM106 is for growing trained tree forms. A classic case of if I’d known then what I know now

The net result has been a vertical hedge of new growth every year that has had to be cut right back in an attempt to maintain the stepover form. Wiser, more sensible heads would no doubt suggest that I cut my losses, dig out these two trees and re-plant something more stepover-suitable. Nevertheless, being a stubborn so-and-so, I’ve persevered with both of them and was rewarded last year when the ‘Howgate Wonder’ produced a pair of the largest apples I’ve ever harvested; each of them over half a kilo in weight.

The third tree is a much more sensible ‘Keswick Codlin’, on either M9 or M27 (dwarfing) rootstock, I can’t quite remember which as I lost the original label years ago. It’s much better behaved and has fruited well for the past couple of years, although last year wasn’t as good as 2020, when the conditions were particularly favourable.

Here’s what I’ve done with the three trees this year:

1. Blenheim Orange

The ‘Blenheim Orange’ put on a lot of growth last year, as it usually does, but only produced a single apple[2]. Here’s another angle, showing quite how much of a hedge I had to contend with[3]:

A lot of strong vertical growth there – some of it three feet or more in length, all in a single growing season – and there are a lot of horizontal branches as well, most of which are blocking access paths either side. Plenty of examples of the classic re-growth pattern as well, with multiple new stems breaking out from the buds just behind the previous year’s cut-point:

Obviously this much regrowth isn’t ideal, but it’s recoverable with some slightly aggressively hard pruning. Here’s the same re-growth section after I’d cut it back:

As you can see, I’ve cut two of the stems right back to the collar – the ring of wrinkled-looking tissue at the base of each stem – which will help promote rapid healing and the growth of the sort of healthy scar tissue you can see in the centre of the photo, where last year’s pruning cut has healed over perfectly. The hollow in the centre is perfectly normal; the tree develops scar tissue over the outer edges of the stem to seal off the cambium tissue – the water, nutrient and sap-transporting outer section – but not the centre of the stem, which is mostly woody tissue and not so prone to rot or infection.

The other two stems have been left as stubs, cut just above an outward-facing bud to direct any regrowth outwards and hopefully avoid too many crossing branches. Having said that, I’m hoping that the dormant buds around the base of the stems will break into fruiting buds, helping to kick-start a new section of fruiting spurs[4].

The rest of the tree was hard-pruned in the same manner, with badly-placed or excessive stems removed completely, and anything with the potential to (hopefully) develop into a fruiting spur cut back to a stub. I also left one or two examples of long brindille shoots that had grown out from last year’s bourse sections:

The bourse is the technical term for the ‘knob’ at the base of the long shoot (at the top of the photo, coming off the main branch). A bourse forms behind a growing apple, or cluster of apples; an anchor-point for the developing fruit. A fully-formed bourse also contains new buds that will sometimes produce fruit buds, blossom, and then a subsequent second bourse the following year, which is how strong bourse-on-bourse spur networks develop.

Alternatively, the bourse might produce a stem known as a brindille. According to some of the pomology theory I’ve read, a long brindille (over two inches) will usually produce a fruiting bud, whereas a shorter brindille (one to two inches) will often produce vegetative re-growth instead; new extension stems. True to the theory, here’s the same bourse and long brindille on April 22nd:

Beautiful, isn’t it? It’s worth bearing in mind that if I’d followed the standard summer pruning advice – which tends to be to cut back all new growth to three buds out from the base in order to encourage fruiting and/or spur formation – I’d have trimmed that brindille shoot and removed the fruit buds at the tip. Instead, I’ll now be able to let that blossom cluster develop into fruitlets, thin it to a single apple later in the year, and when that apple grows it should bend the stem downwards, encouraging the development of more fruiting buds back towards the bourse as that section of wood matures. I should then be able to trim back the stem next winter, leaving a section of fruiting wood for next year: a ready-made fruiting spur, without the extra year or two’s wait[5].

I’ll see if I can track that stem and blossom cluster through the year, to see how it develops. In the meantime, here’s the tree as I left it, post-pruning, back in January:

Not the easiest photo to study in detail (although you should be able to enlarge it by clicking on it), but hopefully you can see I’ve taken that mass of regrowth completely back, either flush to the two main branches or back to short stubs, which I hope will develop into fruiting spurs:

Here’s part of the right-hand section of the tree, with blossom just starting to open, on April 17th:

Assuming the blossom is successfully pollinated and we don’t suffer a late frost like we did last year, I’ll need to thin out each fruitlet cluster down to a single fruit, some time in May or June.

I’m also experimenting with allowing the leading stem at the end of the two horizontal branches to continue to grow. I’ll be tying them in to stout canes at either end of the tree and encouraging them to develop vertically. I’m vaguely hoping that this will help to focus some of the vegetative regrowth into these upright stems, which I can then prune back to a suitable height next year. Alternatively, I might just end up with two more sections of hedge at either end of the tree and be forced to trim them right back to the original horizontals. It’s another try-it-and-see experiment, which might work, or might not. Time will tell.

2. ‘Howgate Wonder’

The similarly-vigorous ‘Howgate Wonder’ also put on a significant amount of growth and, as already mentioned, produced two enormous apples (pictured at the top of this post). Here’s the tree before pruning in January:

It’s not quite so hedge-like as the ‘Blenheim Orange’ but again, that MM106 rootstock had fuelled a lot of regrowth, all of which had to be removed. The principles and procedure were the same: take everything back either to the point of origin, with a cut just above the collar; or leave a stub, with a cut just above an outward-facing bud, if it looked as though it might have a chance of developing a fruiting spur in future seasons.

Here’s the end result (again, click the pic for a larger version):

And here’s a close-up of one of the sections of fruiting wood, with potential fruit buds[6] hopefully ready to break and bloom:

I look forward to seeing whether this tree produces enormous apples again this season, or whether it spreads its energy more evenly between these developing blossom clusters:

3. ‘Keswick Codlin

Finally, having said that this ‘Kewsick Codlin’ on dwarfing rootstock is much better behaved than its fellow stepovers, it seems that it still put on plenty of regrowth last year:

This tree has been fruiting well for the past two years – dwarfing rootstocks tend to encourage early fruiting – although 2021’s crop was smaller than 2020’s, as was common across our site.

Again, the pruning plan here was simply to cut back the lengthy stems to either the collar or to leave a stub. Here are before and after pruning pics of a particularly crowded section of growth that’s placed just above the main stem:

And again, I left a brindille or two but cut everything else back either to just above the collar, or to a stub. I seem to have neglected to take an ‘after’ pic of the tree back in January, but here it is on April 17th, cloaked in blossom and – with luck and good weather – ready to produce a bumper crop again this year:

End Notes

So there we have it. The winter-only pruning regime continues, and seems to be producing good results. What I’m hoping to demonstrate here is that the standard mantra that trained forms of fruit trees must be pruned in summer in order to “encourage fruiting” – which is what a lot of the pruning manuals and general gardening books will tell you – isn’t necessarily true.

I’m not saying that summer pruning is wrong – although some of the research I’ve read has highlighted a number of potential issues that the practice can cause[7] – but I hope that my three blog posts on the subject have demonstrated that summer pruning certainly isn’t necessary, even for trained trees.

In the meantime, if you have any thoughts, questions, or pointers to add, please feel free to do so, via the comments. (If it’s your first time commenting then I’m afraid the system will hold your comment until I have a chance to manually approve it, but I’ll drop you a line to let you know when it goes live.)

Footnotes

Footnotes
1 For more info on different types of rootstock, have a look at this highly useful overview on orangepippintrees.co.uk
2 Last year was not a good year for fruit in our neck of the woods, with a hard frost in May doing a lot of damage to the blossom on our site. Besides which, this particular tree had only been in the ground for three years at that point, so was barely reaching maturity.
3 Ridiculous, isn’t it? But, knowing how vigorous the tree is and how much regrowth is likely every year, it does allow me leeway to monitor the effects that hard pruning have on this sort of tree, which means I don’t have to experiment with the standards in the Plot #79 orchard. It’s all a valuable part of the ongoing learning process as far as I’m concerned.
4 Although knowing the vigour of this particular tree, it’s more likely that I’ll be cutting back another three feet of new stem next year…
5 I’ve been planning a blog post or three on the science of summer pruning for a while now, but probably won’t find time to write anything up until next winter. New full-time job just started, allotment season hitting its stride, lots to do in the garden… research will have to take a back seat again until the end of the year.
6 At this stage they’re only ever potential fruit buds. If conditions aren’t right at blossom time – the wrong temperature, insufficient water or nutrients, or if there were too few chill hours the preceding winter to initiate bud development – then an individual bud could easily remain dormant for another season, or develop into a vegetative stem instead.
7 Again, I’m planning to explain this in much more detail in a series of blog posts, but they’ll have to wait for now…

4 comments

  1. summer pruning triggers less vigurous regrowth than winter pruning. so in addition to you current practise you could break away some new growth in summer. it will heal super fast and your winter pruning will be a bit easier.

    1. Hi Bert –

      Summer pruning is something I’ve been meaning to look into in depth for a while now. The initial reading I’ve done suggests that the restriction in regrowth vigour is due to the reduction in late-season photosynthesis due to leaf removal. But this also reduces the rate at which fruit ripens, leads to a reduction in late season secondary growth (thickening of the trunk and branches) and also reduces the tree’s capacity for nitrogen storage over winter, which then has a direct impact on successful bud development and blossom the following spring. That’s not the whole story though, it’s an awful lot more complicated than that. As I say, I really need to do more research, which I probably won’t have time for until this winter at the earliest… which will be too late for summer pruning season 😐

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