Pruning Time

General Fruit Growing
#21

Just a bit of TMI on the role of apical meristems:

Each bud, whether shoot, lateral, or adventitious, and whether limb, flower, or leaf has an organized growing region called the apical meristem that provides for the growth in length of these structures.

The degree of apical dominance determines the degree of activity of the buds (lateral buds) below the apical, or branch tip, bud. Trees with strong apical dominance restrict the growth of these buds and have a single trunk as seen in a fir tree whereas trees with weaker apical dominance are highly branched because buds closer to the shoot tip can sprout as seen in an apple tree - apical dominance is still there, just weaker. Apical dominance is maintained by hormones released by the apical bud that move down the branch to inhibit activity by the lateral buds. The further down the limb, the less the influence so buds further down the limb may begin to grow. Cutting off the limb tip removes the apical dominance influence of the apical bud on that limb which then allows for all the buds along that limb to become active.

In Spring pruning, growth is vigorous and a very large number of buds including water sprout buds may start rapid growth. This is potentially a good effect IF you need new limbs in new positions to rebuild a treeā€™s shape. But, having to prune off a lot of unwanted limbs increases the opportunity for disease.

In Summer pruning, removing a portion of a limb and the included apical bud has a far less dramatic effect. This is because all those lateral buds below the cut are already entering dormancy. Most of these buds will remain dormant until the following Spring. But, following the Summer pruning, buds near the tip of the pruned limb (near the cut) will themselves establish apical dominance and control the buds below them on the limb when growth starts the following Spring. So, the following Spring, far fewer buds will become active and, therefore, far fewer new shoots will form. This means less growth, less pruning, and less opportunity for disease to enter.

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#22

All Iā€™ve been talking about is managing trees exclusively by summer pruning- that is the evidence and research i was asking for

I never suggested that some summer pruning isnā€™t useful- I advocate pruning in all 4 seasons for different reasons and results and donā€™t suggest you only prune in winter for a single species I grow. In areas with canker, I donā€™t endorse winter pruning for peaches or cherries at all, and even when canker is not an issue, only when fear of extreme weather is past. I prefer pruning peaches sometime between first growth and full bloom when I have time for it, but I cannot wait until then to complete pruning most of the orchards I manage and Iā€™ve not suffered canker problems as a result of pruning dormant peach trees. I have suffered cold damage, however, when temps dropped into single digits immediately following pruning- but only on very young trees. Older trees in the same orchard suffered no damage, but the experience left me very wary. In my area, single digit temps are not uncommon in March.

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