When is the best time to prune?
On warm, sunny days in January and February, I itch to be out in the garden, so I
often turn to pruning. However, last winter, I felt like my wintry
pruning bout may have been responsible for killing off the spring shoots
of our everbearing raspberries, so this year I decided to research
Unfortunately, the conclusion I drew after reading several scientific
articles was...it's complicated. Winter hardiness is affected by a
variety of factors, including how dormant the tree is at the time, the
recent air temperature, the plant's maturity, and more. So, although
most orchardists agree that fall pruning will lower your fruit plants'
winter hardiness for months afterwards, few are willing to go out on a
limb and give you a firm date after which it's safe to prune during the
dormant season. In fact, the data made me wonder whether, from a tree-health
point of view, you wouldn't be better off waiting to prune until after
the tree's flowers have opened in the spring.
On the other hand, pruning not only makes a tree less winter hardy; it
also makes the tree's flowers more sensitive to cold. Critical temperatures
peach blossoms, for example, can vary by as much as ten degrees based on
factors that include the temperature just before the freeze and whether
the tree has been recently pruned. So maybe we really shouldn't
be winter pruning at all and should stick to the summer pruning and
training that has become much more of a staple on our farm.
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But, on the third hand, there's just so much more time for careful
pruning at this time of year than there is in the summer when every
plant is breathing down my neck and asking for attention. So, I'll
probably winter prune anyway, maybe taking Lee Reich's advice of pruning
in February, or following the Iowa State University guideline of
pruning between late February and early April. Because, after all, we do have
to compromise between what's best for us and what's best for the trees
--- and what's best for me is to enjoy pruning under the winter sun
before the vegetable garden begins to consume all of my attention.