There is a strange type of homeowner out there where nothing has been pruned on their property for years. You may not feel any older than the last time you manicured your shrubs, but that year you missed was really a decade or two ago. Even though it’s been part of a century since anything but your lawn was cut, you are the fussy type. You want things done right, meaning no pruning until it is ideal for the plant. Your mother always said that pruning in the wrong season could reduce the bloom, so let’s be careful and not remove a single bud from that rhododendron the size of a one-car garage outside your kitchen window.
All kidding aside, when is the best time for pruning and why? There is a short and a long answer. The short answer is that if your landscape looks like the one described above, prune now. Clean the place up and keep reading.
The long answer for proper pruning time varies according to plant species and two possibly conflicting criteria are involved. The first is to ask what is best for the plant’s health and the second is to ask what is best for the plant’s appearance.
In the first case, understand that a plant creates and uses its leaves to eat. It’s a risk and reward proposition. In the spring, in the hopes that it will gain an energy return, the plant uses energy reserves to produce its leaves. If those leaves are immediately removed, either by you or by a chewing insect, the plant receives an energy deficit. In terms of leaf production, it is best for the plant if you wait until the leaves have done their job and have fallen off the plant in the fall. It is also easier to see the form of the plant without the leaves. Simultaneously, pruning exposes the plant to additional disease risk, so the dormant winter season is also safest for the plant from a disease perspective.
Otherwise healthy plants are resilient and that is why pruning professionals can, in good conscience, perform pruning year round.
On the other hand, when the plant’s appearance is key, pruning should be done as soon after its most valued seasonal show is finished. In other words, in the case of a burning bush, its fall color is prized. Removing leaves in mid-summer will reduce the fall show. On the other hand, pruning a lilac in late fall or early spring is certain to reduce the amount of fragrant blooms next Mother’s Day. Fruit trees should be also be pruned after bearing; otherwise you will remove what the late frost left.
Finally, some plants like spirea will double bloom if pruned by mid-summer. For pruning, you should know your plants and prune accordingly.
Joshua Arp is an ISA-certified Municipal Specialist, a Clarks Summit Tree Commissioner and an operator of a landscape maintenance business. He can be reached at firstname.lastname@example.org.