North American Fruit Explorers mailing list at ibiblio

["Michael Phillips" <michael@herbsandapples.com>]

This won't explain all such mysteries by any means, Alan, but it's probably
an integral factor:

Both the pollen grains and particularly the seed ovaries of the flower are
viable for a limited amount of time. The bees deliver the pollen to the
sticky sigma which then moves down to the seed ovary by way of the tube-like
style. This "pollen tube" develops faster in warmer weather. . . and slower
in cooler weather. That explains why sometimes a "good pollination day"
followed by several days of much cooler weather doesn't result in much fruit
-- viability is lost in the seed ovary before the pollen gets there.
Additionally, when pollen comes from another variety, this pollen tube
develops faster, thus giving cross-pollination a leg up in this respect.

Lots of cloudy weather immediately after bloom plays a role here too.
Photosynthesis is critical for "firming up" the deal so "last minute"
fruitset isn't abscised. Pollen being delivered to all the seed ovaries on
apple and pear is a part of this too.

But those single well-set branches on an otherwise barren tree are beyond me
as well!  

Michael Phillips
Lost Nation Orchard
859 Lost Nation Road
Groveton, NH 03582
(603) 636-2286
www.HerbsAndApples.com 
www.GrowOrganicApples.com 
 
Date: Sat, 2 Jul 2011 05:03:14 -0500
From: Alan Haigh <alandhaigh@gmail.com>
Subject: [NAFEX] Mysteries of fruit set
To: nafex@lists.ibiblio.org
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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
category.

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