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  • From: Stephen Sherman <spsherm@msn.com>
  • To: permaculture <permaculture@lists.ibiblio.org>
  • Subject: Re: [permaculture] fruit trees
  • Date: Sat, 29 Dec 2012 22:40:04 -0700

Apples (pomme fruit in general) can tend towards biennial fruiting. Most modern varieties have been selected to minimize this trait if not eliminate it. However it is still present. If you look at the variety descriptions from growers who have a large number of the older varieties, there are still a few who are noted for tending to biennial fruiting. And fruit thinning definitely help suppress this tendency.

I suspect it is an issue of tree resources. During the second half of the summer and fall, when this year's fruit is growing and ripening, the tree is also forming fruit buds for the following year. Current seed production would appear to take priority, to the detriment of next year's fruit buds. Which would explain why thinning this year's fruit can reduce or eliminate the tree's tendency to skip fruiting next year.

From my own observations, I had an apple tree which was half burnt in a wild fire. This tree had been a regular yearly bearer, however after the fire it had no flowers for a year, even on the side which was not damaged by fire. The following years (so far) it appears to have returned to yearly bearing. It would appear that any severe stress on the tree can cause fruiting to be skipped for a year. (perhaps longer, thankfully I have not had experience with longer stress to the tress)

Steve


On 12/23/2012 10:18 PM, loren luyendyk wrote:
Very interesting thread. From an economical perspective, the issue of alternate bearing is indeed
important to fruit farmers, as it seems that all trees of the same variety in a certain area will follow
the same pattern seasonally. In my experience, avocados (Hass) typically have "on" and
"off" years which is represented regionally, and this trend can affect market price
significantly. An "on" year creates a glut and low market prices, as everyone has a bumper crop
that year. (this trend is more complicated now with the importation of foreign fruit) Alternate bearing
can be pretty extreme with avos, with harvests ranging from 15,000 lbs/acre to 2,000 lbs/acre.

However, if you had Hass avocado trees (the variety is important in a commodity market)
that were unaffected by alternate bearing, you would be a happy farmer. You would have
above average harvests during "off" years and your crop would demand a higher
price, as a result of limited supply. I imagine plant breeders have tried to get
around this one, but I am not sure (anyone know?).

The process of "thinning"- removing small fruit- is very common with most
stone and pomme fruits, mainly because if you remove 1/2 to 2/3 of the fruit you will
get larger fruit (and we all know that bigger is better :) Thinning is not feasible
with avocados as the trees are usually too tall, and they tend to drop excess fruit
during the year on their own accord. I have never heard that thinning was an attempt
to disrupt alternate bearing. Also, in my experience thinning is mainly practiced on
deciduous trees.

>From and evolutionary biology perspective, I am not too convinced of the predator
satiation hypothesis- this appears to be a Darwinian approach based on competition. I
agree that the more fruit a tree produces the more the animals will plant it (not just
squirrels but birds), and it would be a "reproductive advantage" to have more
fruit every year.

I think alternate bearing (in some trees at least) is based more on weather
(and possibly that the tree simply needs rest after a big year). Here in
Southern California we can tell if we are going to have good winter rains if
the coast live oaks set lots of acorns. The trees seem to know that there
will be good conditions for their fruit to grow into new trees and they pump
them out.

Loren Luyendyk
805-452-8249
Permaculture Design and Education
ISA Certified Arborist #WE-7805A
www.sborganics.com
www.globalpermaculture.com
www.surferswithoutborders.com







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