[NAFEX] fruitset mysteries

Alan Haigh alandhaigh at gmail.com
Sun Jul 3 12:56:32 EDT 2011


Michael, I'm flattered to get a response from the writer of the best organic
fruit growing book I've read and a great gardening book in general.
However, as interesting as your botanical explanation is, I think little of
my various observations are explained by it.  Such as Damson plums a few
feet from each other blooming at exactly the same time in same soil with
same crop load the previous season- one loaded and one with just a few
fruit.

All the orchards I manage got the same cool wet weather and most had bloom
at precisely the same time. Most of these orchards are in northern
Westchester county, just a few miles from each other, at similar elevation
and some at very similar sites.

This is not the first year that plums have set in very unpredictable ways
and they seem somehow to be the most variable fruit I grow as far as
productivity site to site.  Some varieties are much more variable than
others.

This is  Michael's comment that I'm responding to. "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.


Chris wrote "During bloom time we had a number of
freezes that probably affected the lower branches more than the upper ones.
It could be that colder air settled down lower in the canopy"

Chris, In the literature I've often read about lower branches losing fruit
because the coldest air was there or, conversely, being saved by snow
cover.  Losing flowers of one species and not another can also be affected
by timing and not just general hardiness as the hardiness of flower buds
will vary during the coarse of winter and spring.

I have been surprised about hearing of complete peach crop failure in CO
while plums seem fine, but at least I could provide a theory that a cold
event occurred at a point of time when the peaches happened to be more
tender.   Flowers, for instance, are more tender than recently set fruit
IME.  I've had seasons where a frost destroyed most of the flowers of my
later blooming peaches but not the fruitletts of early blooming ones, which
contradicts expectations that late blooming is always advantageous.

Alan Haigh, Home Orchard Co, Z6, southeastern NY


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