Hi all,
I have been a lurker for a while, but I don't post much. I am still fairly new to permaculture, but I am steadily picking things up.
Anyway, I wanted to hear thoughts on an observation/theory I have. I have long been baffled by pruning fruit trees. It seems like the trees know what they are doing, so why would they need our help? I have looked around for answers as to why pruning is so essential (as every mainstream source confidently asserts that it is). I find a lot of articles on how to prune, but almost nothing on why to prune! There is often a sentence or two that says something along the lines of "pruning helps keep your tree healthy and maximizes productivity." That seems counter intuitive to me (though that doesn't necessarily mean that it is wrong). I would expect that trees are naturally productive since fruiting is their means of reproduction. I want to know why this is the case (or even if it is the case at all, since up to this point I have not found any studies or convincing evidence of a measurable difference in yields or health of the tree). There are two good explanations I know of. First, pruning reduces the energy and nutrient requirements by reducing the amount of vegetation (much like removing suckers on, for example, a tomato plant) which promotes more vigorous growth in the remaining vegetation. Second, by opening up the tree more sunlight reaches each individual branch and this promotes more vigorous fruiting. Whether either or both of these explanations is true I do not know.
Additionally, I recently watched the DVD "The Permaculture Orchard : Beyond Organic" (which I thought was excellent by the way, I would recommend it if you have any interest in growing fruit trees even on a small home scale). In it they talk about training the branches downward to drastically reduce the amount of pruning needed. The explanation given was that when the branches grow upward the tree produces hormones that promote vegetative growth. When the branches bend downward the tree produces hormones that promote fruiting. While this may be less labor intensive than pruning, it still involves the orchardist doing quite a bit for the trees, so I still wonder why trees would be so bad at producing fruit on their own if that is how they propagate themselves (one possible answer may be that trees simply don't need very much fruit to propagate themselves, and having more vegetation and less fruit per year is somehow beneficial to that end).
Now for my very limited observations. The house I grew up in has two fruit trees in the back yard, one apple tree (I suppose to be standard size at around 30 ft (4.5m)) and one pear tree (I suppose to be a semi-dwarf at around 15 ft (2.25m)). I do not know the varieties, but they are both decent tasting. I suspect they were both grafted because of the good fruit, but I did not see the typical mark around the base of the tree tell-tale of grafting (but given their age that very well may not be visible, especially to my untrained eye). To my knowledge they were never pruned up until last year when I decided to do so (though now I wish I would have left them alone for more careful observation). At the very least, they were not pruned for the 20 or so years my family lived in the house (they were planted before we had the house though so they may have been pruned when younger by previous owners). Every year they fruit quite well (though I don't have anything unpruned to compare them to, but I always thought they produced a lot of fruit for something we never pruned, sprayed, fertilized, or otherwise did anything to really). They have had no disease problems that I know of.
After watching the permaculture orchard DVD I started thinking about the form of the trees on the property. I realized that most of the branches on both trees were bent downward even though no one had trained them for at least 20 years. This downward bend was especially pronounced on the larger apple tree. Also, older/larger branches seem to bend down much more than younger/newer growth.
So here is my theory based on all of this: perhaps fruit trees have a strategy by which they first send all of their energy into vegetative growth, primarily upwards at various angles. This establishes the tree so that it is more resilient (e.g. wind storms, snow, etc.) and shades out weedy undergrowth by producing a dense canopy (as opposed to the very open canopies of pruned fruit trees. After sufficient establishment, the branches naturally bend downward due to their weight (since they are getting larger and further away from the trunk). When they bend downward this signals the tree to produce the fruiting hormones as opposed to the growth hormones (I know nothing about these hormones, so that is taken entirely from the DVD). As the tree gets older and more and more branches begin to bend downward, fruit production continually increases.
This theory might also explain why pruning is so prominent. Even though (if this theory is right) fruit trees are very productive when left to their own devices, they take a long time to get to that point. When you prune it is much more work but there are more immediate results. If it takes 5-10 years to get full production with pruning, and 20-30 years without, almost any typical commercial orchard is going to be willing to invest the work to get fast results (of course these time frames are very uneducated estimates, so the discrepancy could be much greater or much less).
The implication I am most intrigued by is that if this theory holds true, then you could have a very productive orchard with virtually no maintenance, but it would take a little longer to establish.
Considering these are very limited observations and my very limited knowledge, I am eager to hear about others thoughts and observations. Do you have any observations you could provide which would support or deny this theory? Or perhaps a relevant study or book on the subject?
Thanks in advance!
