Within any plant a push and pull goes on between fruiting an stem growth. Both require energy, which the plant has to apportion between the two. The more vigorously growing a stem, the less fruitful it is.
All this talk of hormones and inherent stem vigor is more than academic; it can translate into delicious fruits.
But pear trees, especially in the youth, tend to put too much of their energies, too much for me, at least, into stem growth. The result is that they can take long time to settle down and begin bearing fruit.
Hence, the strings. I can change my pear trees’ habits by merely tying down branches, reducing the effect of that auxin so that growth is more uniform along a length of the stem. And, as important, slowing growth nudges the energy balance in the direction of fruiting.
More Fruit or More Growth?
Branch bending is not only for coaxing a tree into fruiting. On young branches, it creates a wide angle between a branch and the developing trunk. Wide angles here have been shown to result in good anchorage, sturdy side branches that can carry a weight of fruit.
Suppressing the vigor of side branches also ensures that they won’t compete with the developing trunk, which needs to be top dog.
And using string to play around with plant hormones isn’t needed on every fruit tree. At the other extreme from pear in its growth and fruiting habits is peach. Peach is naturally very fecund, and becomes naturally so at a very young age.
Beauty, Fruit, and Fun
All this concern with auxin, vigor, and fruiting comes most prominently into play with espalier, which is the training of a tree to an orderly, often two dimensional form. The tracery of the branches themselves adds to the decorative value of the plant.
Fruiting espaliers, besides being decorative, produce very high quality fruit. Pruning and branch bending maintain a careful balance between yield and stem growth, and the form of the plant allows leaves and fruits to bathe in sunlight and air.