Is anyone familar with scoring and girdling to increase yield?
http://hortsci.ashspublications.org/cgi/content/abstract/43/7/2022?etoc
Link: hortsci.ashspublications.org/cgi/content/abstract/43/7/2022?etoc
Flowering, and thus fruiting, of a plant is affected by the rate of vegetative growth (the production of new branches, etc). Typically, fruit and nut tree seedlings do not flower until vegetative growth has begun to slow, usually anywhere from the third to the eighth year, but sometimes earlier or later depending on the variety. People are impatient and have devised a number of ways of speeding flowering and fruiting.
One of the most common methods with fruit trees is to graft onto a dwarfing or semi-dwarfing rootstock or to graft a dwarfing or semi-dwarfing interstock on the rootstock and to graft the desired variety onto the interstock. Slowing the vegetative growth speeds the onset of flowering and fruiting. If you look through past issues of the RHA Newsletter (back into the 1970s), you will see various suggestions of ways to decrease vegetative growth and increase fruiting with reluctant varieties: drouthing (providing only the minimum of water to the plant), starving (eliminating supplemental nitrogen fertilization), crowding (keeping the plant in an extremely small pot so that it becomes root-bound), and maybe another method or two. Scoring and girdling work similarly to slow the vegetative growth of the plant by (perhaps) decreasing how much of the food produced in the leaves gets returned to the root and non-fruiting parts of the plant.
I don’t think I would use scoring on any rose I cared about unless I had lots of plants of that variety: the danger of helping to cause canker or other serious problems would deter me, and the scoring causes damage that is not fully reversible.
Girdling with a tight wire or cord might work if it’s clear that the failure to set seeds is not caused by core genetic problems (such as triploidy). Probably no amount of girdling, scoring, drouthing, crowding, or starving will make a plant set seeds if the problem is in the genetics. And you have to remember that girdling is a long-term project. But as a rose hybridizer you already have all the time in the world. 
Applied firmly one year, the girdle would be slowly tightened by expansion of the rootstock during the following years, and vegetative growth would be slowed. If the girdling did not induce increased seed set within the next 2-3 years, the girdle could be carefully removed or at least cut to permit the plant to resume normal growth at its own pace. If the girdle had been overgrown by the bark, removal would probably cause severe damage, so cutting the girdle would make more sense than trying to remove it. With the restriction decreased by cutting of the girdle, growth would increase gradually as the plant established new channels in the non-restricted area of the trunk/stock. Full recovery probably would take about as long as the girdling had been in place.
Has anyone on the forum tried this method?
Peter
Further thought–
Anyone planning to try girdling should remember not to use copper wire.
Peter
Girdling a plant is a very bad idea. The phloem layer, which distributes all of the photosynthate produce by leaves, is barely a few tenths of a millimeter thick. It lies a couple of tenths of a millimeter beneath the surface of a stem.
Flowering is completely under genetic control, and is mediated by hormones.
The most important thing you can do to promote flowering is to grow healthy roses and make sure they are fed appropriately with a fertilizer specifically formulated for roses.
I wouldnt do it regardless of benefits simply because I have no desire to make my plants prone to other things such as gall…
Another scientific study:
http://www.troz.uni-hohenheim.de/research/Thesis/MScPP/Wittmann.pdf
Link: www.troz.uni-hohenheim.de/research/Thesis/MScPP/Wittmann.pdf
“Girdling at the 2 g stage reduced yield and significantly increased fruit size and weight.”
This makes sense. The sugars that would otherwise have gone into root and stem development could not reach there because of the girdling so got consumed in fruit development. Short term gain (though a decrease in yield implies decreased flowering) at the expense of debilitating of the plant.
“Flowering is completely under genetic control, and is mediated by hormones.”
This past summer my fruit trees had almost no fruit–because
the flower buds were killed by a late frost before the flowers opened. I’ve also observed that bulbs such as lilies set buds according to conditions the previous summer. Unless these events are under genetic control, this doesn’t appear to be true.
(though a decrease in yield implies decreased flowering)
A couple of my apple trees set six or eight apples on each fruit spur, and in June the marble to golf ball size apples started to fall to the ground. This resulted in a decrease in yield, but the problem was an excess of flowering and fruit set, more than the trees could mature. I then thinned the small fruit to one per spur. The resulting decrease in yield was the result of excess flowering, and cultural practice, not decreased flowering.
To me it appears that flowering is a multi-step process, and genetics is one–of several–components. The environment, including plant nutrition, weather, pruning practices, culture, etc., also have an effect. “Pegging”, or allowing
a branch to arch up, then be tied down lower than the high
point of the branch, has often been recommended as a cultural practice to increase flowering. It doesn’t change
the genetics of the plant, but it does increase flowering.
Ken