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Last updated on January 21st, 2020
If you have a plum tree it is a common question to wonder when you should prune. The issue here is that the answer is really contingent upon your goals. In general, newly planted plum trees, 1 and 2 years old, should be pruned to encourage them to bush out and form a well-branched tree and established trees should be pruned to control the size, encourage higher yields and remove damaged or diseased branches. Pruning should be done in spring just before bud break out to reduce the risk of silver leaf disease.
When to prune plum trees
If you have a young, small plum tree and you wanted to grow quickly so that it produces a stronger harvest, you are better off pruning early spring to encourage more vigorous growth as we have briefly mentioned above.
But what if you have a plum tree that is grown so large it is already too big to harvest? In that case, summer pruning might be better for you. If you prune your fruit tree during the summer it reduces the size by cutting off many of the branches without simultaneously encouraging new growth. And you can cut off up to 25% per year.
Of course, there are smaller considerations that you must mull over such as whether or not your plum tree is diseased, has broken branches, is producing poor quality fruit, etc.
Why timing matters
It’s important to understand the seasonal cycle of energy that your plum tree has in order to understand when to prune and why the timing is important. Timing in the late winter early spring spurns better growth while timing in the summer does not. Why is this? Fruit trees grow much faster if they have ample energy in the springtime and their growth slows down during the summer months.
It is not recommended to prune in the Autumn because this is the time where your tree does most of its photosynthesis. During the summer your tree is able to convert the light from the sun into sugars and store those sugars into its leaves but as the weather starts to cool and Autumn arrives, your tree is preparing for dormancy and to do that it has to move those sugars from the leaves down into the roots. If you cut and prune in the autumn you run the serious risks of cutting off the branches with the leaves storing that energy necessary for the roots. If that happens the energy never gets to the roots in your plant and may be unable to support itself. Simultaneously, if you live in a cold climate during the Autumn your tree won’t have the energy to heal its wounds that are caused by the pruning process.
During the winter your tree goes into dormancy. The tree itself hardly grows above ground but the roots continue to grow below. A great deal of the energy amassed during the summer and Autumn is stored in the root system. If you live in a colder climate this is the perfect time to cut your tree as it won’t have fruit, flowers, or leaves on it so you’ll be able to much more clearly see the structure of your tree. Doing it at the end of winter is better than the beginning of winter because it allows your tree to better heal from any cuts. Moreover, it also spurs more vigorous growth the coming year because you are selecting only the best branches to produce fruit and you are removing any lower-quality branches. Your tree has a finite amount of energy in it and now that energy can be put into a selected 35 branches that are strong and healthy rather than 50 branches some of which are healthy and some of which are not.
As spring emerges the weather gets warmer and your tree awakens from its dormancy. The energy stored during the winter gets used to power that new growth. This is an opportune time to just take a look at your tree and prune any branches that simply did not survive the winter. This will not encourage as much growth as if you prune at the end of winter because some of that stored energy has already been used but if you want to make your plum tree more compact this is the perfect time to do it.
Once spring slows down and nutrients get stored in your plum tree your tree needs to rest for the rest of Summer to rebuild that stockpile. With the leaves fully developed it will start to produce energy through photosynthesis and use that energy to slowly grow over the summer and drive back into the roots for winter. Summer pruning does bring with it many benefits as a result. Vigorously pruning during the summer will reduce the size of a much larger plum tree and it’s the perfect opportunity to remove crisscrossed or rubbing branches, broken branches, or diseased branches.
Pruning diseased plum trees
If your plum tree is showing signs of disease you can prune it anytime, don’t wait, remove them as soon as possible. Winter is typically the easiest season in which to notice the diseases and if you choose to wait until the end of winter to cut away the disease branches it will help your tree to heal faster. However there is the risk that some diseases are dormant in the winter and if you notice serious diseases like black knot or fire blight, you don’t want them spreading within the tree or to nearby trees so you will need to prune immediately regardless of the season.
How to prune plum trees
Pruning is essential to the health and longevity of your tree but you have to make sure you do it at the appropriate time. Just as important is doing it correctly. If you don’t prune your plum tree correctly you can actually hurt it. You will need a sharp set of loppers and possibly a pruning saw depending on the size of your tree. If your tree is quite large you will need a sturdy ladder so that you can climb up and reach the top branches. Again you can cut off about 25% of the tree each year if it is large and mature and that will help to keep it smaller and contained without doing any damage. Otherwise, you can cut away the sick and dying branches, any branches that are rubbing against one another and preventing proper airflow, and those which you notice are already hanging too low on to the weight of your fruit. We also recommend pruning off any branches that didn’t produce any fruit in the current year.