Should Geranium Shoot Growth Dictate Pruning?

I hope you can make out the strong new shoots which have grown from the collapsed stems (due to growing too fast) of this geranium. The point here is they have grown in the gap without any encouragement (the stem has not been cut back), almost certainly because the spot has received unrestricted sunlight; nodes further up the stems, which are in the shade because they are behind other stems, have not developed. This looks like phytochrome at work again.

Of course, it could just be coincidence. And, strangely, I have never before noticed such a response. But if new shoots have a preference for non-shade, then it will pay to prune accordingly. In other words, the plant can be pruned into a conical rather than a mushroom shape, thus helping ensure all new buds are free from shade.

Note that when a stem collapses into a horizontal position, the dominant effect of the apical bud is removed and the axillary buds lower down the stem are able to develop (they were previously restricted by auxin produced by the apical bud) into several upwardly-growing new shoots. This effect can often be seen on fallen trees which still have some roots left in tact.