So, you’ve developed an idea about what needs to be pruned, now you need to figure out when different plants should get pruned. While I’ve addressed a little of that in the previous sections, let’s talk about it generally here.
A good rule of thumb (though not universally true) is to chase flowers with the pruning shears. In many cases, the best time to prune a plant is right after it flowers, for various reasons.
Flowering shrubs are a good example of this. In general, the best time to prune a flowering shrub is right after it blooms for the hear. Again, not universally true, but it’s a good rule of thumb. Lilacs bloom in May here along the front range in Colorado, so I prune my lilacs as soon as the blooms start to look ragged. Forsythia blooms earlier in the spring, so if I were going to prune a forsythia, I’d do it as soon as the green started to cover the yellow (not that there are many times when I’d prune a forsythia… I’m just sayin’…
I’ve talked before about root hardy perennials that need to be but back to the ground in the spring, such as butterfly bush here in Colorado. I won’t go into that in this article – here I want to talk about the more traditional pruning.
Most deciduous trees can be pruned just about any time. Personally, I favor pruning in the spring and late summer for most trees. By selectively pruning in the spring, I choose where I want the tree to send (and not send) energy for growth. This lets me define the shape of the tree as it grows, and avoids energy being wasted building unhealthy or unattractive growth that probably needs to be removed later. It also promotes more rapid growth, as the growth is less random and more focused.
My fall pruning has some of the same objectives as the spring pruning, though I’m really a bit more focused on preparing the tree for winter. I want to clear out branches that are likely to suffer from ice and snow in the winter, leaving the most healthy and attractive shape possible.
I want to mention problem trees here as well. The best example in our area is the Russian Sage. Considered by most people to be a “weed tree”, it was once planted throughout the suburbs as a hardy specimen tree. It has thorns, is unwieldy, and self-seeds abundantly. In many places planting them is actually outlawed.
However, if you’ve got a Russian Sage already growing that you don’t want to remove, there’s some good news for you. A Russian Sage can actually look very nice, provided you’re willing to spend the time pruning it. Not just in the spring or fall, but as often as once a month. The first time you get in and clean it up will be an ordeal, but if you stay after it in little chunks throughout the growing season thereafter, it’s far more manageable.
Another tree that we actually plant fairly often is the Ginella Maple, or Amur Maple. It has a fairly weedy style of growth, but if you stay after it 2 or 3 times a year, you can maintain a really nice tree that – if pruned right – actually resembles the beautiful Japanese Maples that our climate doesn’t allow.
On the other end of the spectrum are the trees that require rare pruning. Many of the oaks and hard maples fall into this category. Once you’ve got them pruned up to the height you want, their habit keeps them shaped for both good looks and health for the most part.
The important thing to remember is this: pruning mistakes are generally on the side of neglect rather than excess. Keep a set of good shears with you whenever you walk through your gardens – it’s almost certain there’s something that needs a bit of pruning…