[NAFEX] Mysteries of fruit set

Alan Haigh alandhaigh at gmail.com
Sat Jul 2 06:03:14 EDT 2011

It’s funny how often what you read about fruit trees doesn’t explain what
you see in the real world of your own orchard.  The latest example for me is
the issue of fruit set.  If a tree doesn’t set a crop either it didn’t get
pollinated, didn’t produce flowers to be pollinated or there was a
nutritional deficiency that rendered the tree unable to produce fruit.  That’s
what I generally read about fruit set.

This season seems to be setting those neat explanations on their heads in
the orchards I manage.   Consider a tree where there is almost no fruit
except on one or two branches and those branches are completely overloaded.
I’ve seen this with scaffolds pointing in every direction, so the issue
clearly isn’t light related.   Such trees flowered throughout and were
tended by bees throughout but there the fruit is – all bunched up in a
couple of branches.

Another mystery this season is how differently same varieties are performing
on different sites- particularly plums.   Methely has always been a
consistent bearer for me- its issue is typically setting too much fruit
where it clusters up like bunches of grapes- but not this season.   This
year most trees on many sites only have a few fruit and yet in my personal
orchard and a few others, the set is exactly as usual-I’ve been back to thin
mine three times.   In fact in my orchard, plum set is about normal except
that Elephant Heart hardly set anything as is the case in every other
orchard I grow it.  My EH tree had plenty of flowers and attending bees and
other plum varieties all around it set very well.

But this is just the beginning of strange occurrences I’ve witnessed this
season.   The Damson plum is consistently a heavy producer of tiny plums.  It’s
not a fruit I bother to thin and yet the tree will push out a continuous
cluster of plums along most every branch every year- until this one.  On a
site where I have three Damsons two are almost loaded and a third, of equal
vigor and health and only twenty feet from one of the other two has only a
few fruit in the entire tree.

The weather this year included a very long period of cool wet weather
shortly after last apples lost their petals.  Wild pollinators were in short
supply but there were just enough warm days during bloom for them to get the
job done in most places.  I was discussing fruit set with a commercial
grower  a short while ago and we both believe that at least some varieties
need warm weather during the first couple weeks of fruit set to gather the
necessary energy to hold on to the fruit.  In fact, some fruit varieties
that are self-fruitful in warm springs need to be cross pollinated when and
where springs are cool.  Apricots and pears seem to generally fall into this

This may be a partial explanation of what went on this spring but all the
orchards I manage had just about the same weather and some  within walking
distance (or bee flying distance) of each other.  I have never had a year
where fruit set was so varied from site to site, tree to tree and even
branch to branch.

Alan Haigh, zone 6, southeastern NY

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