Pruning to Thin the Crop

We have come to the conclusion that hard winter pruning is the best way to thin our crop. Lime sulphur certainly works, but it doesn't feel right.

We "single line" downward hanging branches coming from the trunk (Upright branches are pulled down and tied with string, or totally removed if they are too strong). Our trees are on dwarfing/semi-dwarfing rootstocks spaced 1 to 2 metres apart down the row.

If we have a block we know is due to have a heavy flowering in spring, we winter prune it really hard and thin out the fruiting sites. It seems to us that trees waste a lot of energy producing all those flowers in the "on year". We like to get rid of the flowers before they appear, so the few remaining will be stronger, and hand thinning of fruit later in spring will be more efficient. The idea is to thin fruit buds in winter, not flowers in spring.

Has anybody out there tried this approach, and does it work on large wide-spaced trees on vigorous rootstocks?

Kalangadoo Orchard
On the “other side” in South Australia



Edited 2 time(s). Last edit at 06/12/2013 12:45AM by Michelle & Chris McColl.

This is interesting, because I do the opposite...
We also raised this during the last Berkshire meeting if some remember.

I agree that short term, a heavy winter pruning would reduce the number of flowers, and hence provide some thinning.

But I look at this with a longer term view, with the objective of reducing biennalism...

Often, trees will have more growth on the "on" years than during the "off" years. And heavy winter pruning does induce a growth reaction from the tree.
So my principle is that if I do some heavy pruning on a tree the winter before this tree is due for a weak bloom and little growth, I agree I'll reduce the number of flowers on that year, but I'll also induce more growth on that year, and this new growth will bear flowers 2 years later. I have been successful in reducing the biennalism of some trees (but not all) with this strategy.

Hence, by doing what you do, I would be afraid you encourage biennalism in long term.

Claude

Jolicoeur Orchard
Zone 4 in Quebec

Interesting and confusing, Claude!

Our trees put on more vegetative growth in the "off year", and there is very little vegetative growth in the "on year" when the tree is putting all its energy into producing a mass of flowers and an excessive amount of fruit.

We have to admit when we read "Biennial Resurrection" on page 129 of "The Apple Grower" a few years ago, we were really confused! Have read it again just now - and still having trouble reconciling with what we see here.

When we prune hard coming in to the "on year", we are removing fruiting sites and we also see dormant buds push out of the bark along the branches. Some of these develop into fruit spurs for the following year, which would otherwise be the "off year".

We barely prune the trees before flowering coming in to the "off year", figuring we will need every fruit bud we can get. Once we can see where the flowers/fruitlets are, we may do a light pruning to open up the tree, because we know there will be plenty of growth because there is not much of a crop to slow things down.

Is the difference between what we see and what you see because of rootstock/tree vigour, or is it something else?

Kalangadoo Orchard
On the “other side” in South Australia



Edited 1 time(s). Last edit at 06/13/2013 04:40PM by Michelle & Chris McColl.

How interesting!
I also went to read page 129... and it does describe my reality. I first read about that in a French book on arboriculture about 25 years ago, and have talked about it here and there since.

Now, why would it be different in Australia? Could it be that because your growing season is much longer, you can have fruit buds on the following year on a growth shoot? Or maybe because of varieties that don't behave the same?

As I said, for me this doesn't work with all. It has improved many, but a few seem to resist... Maybe these varieties fruit on the first or third year on a shoot - instead of on the second.

The other interesting thing is on the growing - I see that on a off year, the tree is resting, not producing fruit, nor much wood, while on a on year, the tree produces both fruit and wood.

Claude

Jolicoeur Orchard
Zone 4 in Quebec

It would be good to get to the bottom of this! A few of our observations that may help someone to work out what is going on:

(1) we commonly see a double flush of flowers in the "on year". The first flowers to open come from fruit spurs that are on wood that is two years old or older. Then a few weeks later, we get a second flush of flowers along the full length of one year old shoots (i.e. shoots that grew in the previous growing season), that are generally 30 to 50 cm long - shoots totally white with blossom from top to bottom. The fruit that develops from these flowers on one year old wood is smaller, rounder, has a longer stalk, a smoother skin finish, inferior taste and matures later than fruit on the older wood. This is certainly seen on Gala, Braeburn, Ribston Pippin, Jonagold, Pink Lady, Prima and Sundowner, to name a few.

(2) we have never noticed this type of flowering on one year old wood in the "off year".

(3) weak one year old shoots that are up to 15 or 20 cm long will often form a fruit bud and set fruit on the terminal bud, but not on the intermediate buds. This is certainly seen on Fuji, Pink Lady and many others. In an "off" year with Pink Lady, almost all fruit comes from terminal buds. Fruit from this one year old wood appears normal, unlike the fruit described in (1) above.

(4) fruit spurs can be forced to develop from dormant buds beneath the bark on old wood if the tree is pruned hard in winter.

(5) sometimes biennial bearing is seen within the one tree - the top of a tree is "off" when the bottom is "on", or one side of the tree or one branch on the tree is out of sync with the rest of the tree.

Does latitude have something to do with it? Does anyone of you in the Northern Hemisphere closer to the equator than Claude or Michael see what we see? (We are 37 degrees South, which puts us in southern Spain or maybe Virginia if we swapped hemispheres).

Regarding length of growing season , we reach green tip in early September, and harvest the latest varieties in late May/early June, i.e. approximately 9 months (earliest varieties are harvested in mid to late January, i.e. four and a half months from green tip).

Kalangadoo Orchard
On the “other side” in South Australia



Edited 1 time(s). Last edit at 06/15/2013 02:47PM by Michelle & Chris McColl.

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Then a few weeks later, we get a second flush of flowers along the full length of one year old shoots (i.e. shoots that grew in the previous growing season), that are generally 30 to 50 cm long - shoots totally white with blossom from top to bottom.

I've never seen anything like this.

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weak one year old shoots that are up to 15 or 20 cm long will often form a fruit bud and set fruit on the terminal bud, but not on the intermediate buds.

but I do have some of those once in a while. Usually, they are shorter than that however.

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Regarding length of growing season , we reach green tip in early September, and harvest the latest varieties in late May/early June, i.e. approximately 9 months

There is the huge difference! Here I'll have green tip by end of April or beginning of May, and latest varieties harvest by end of October, so 6 months, a full 3 months shorter than your season. I can easily imagine that giving 3 extra months on the season, a 1 year shoot then has a lot more time to produce flower buds on its length before it starts hardening.

Claude

Jolicoeur Orchard
Zone 4 in Quebec

Great thread!

Nat Bouman
Growing cider varieties in Zone 5b
On B.118 at 18X24
Susquehanna County, Pennsylvania