A pruning calendar for shrubs, trees and fruit that actually holds up
Most shrubs that quit flowering were pruned at the wrong moment, not pruned badly. One question sorts nearly every plant in the garden into the right month.
A shrub that gets tidied up every year and never flowers is not being pruned badly. It is almost always being pruned in the wrong month.
The technique side of pruning is worth learning and takes about ten minutes to explain. The timing side is what separates a plant that flowers hard every June from one that has put out nothing but leaves for four years running, and it comes down to a single question you can answer for almost any shrub without knowing its name.
Old wood or new wood
Some plants form next year's flower buds during the previous summer, on the growth that hardened off that season. Cut those stems off in winter and you have thrown next spring's display in the compost. Other plants form flower buds on shoots produced in the current season, so cutting them hard in late winter costs nothing and often improves the show. Everything else follows from which group a plant is in.
| Forsythia, lilac, weigela, mock orange, deutzia | Flowers on old wood. Prune within a few weeks of the flowers fading |
|---|---|
| Flowering currant, spring-flowering spirea, kerria | Old wood. Same rule: cut it as the display ends |
| Butterfly bush, panicle and smooth hydrangea, caryopteris | Flowers on new wood. Prune in late winter before growth starts |
| Russian sage, late-flowering clematis, most shrub roses | New wood. Late winter or very early spring |
| Bigleaf hydrangea | Mostly old wood. Deadhead only, unless the label says it reblooms |
If a plant is not on any list you can find, use the shortcut: anything that flowers before about midsummer is flowering on last year's wood, so prune it as soon as the flowers go over. Anything that flowers after midsummer is flowering on this year's wood, so prune it in late winter. That single sentence gets the great majority of garden shrubs right.
What you can cut in any month
Timing rules govern flowering wood. A short list of cuts is fair game whenever you notice the problem, because leaving them costs more than the cut does.
- Dead, damaged and diseased stems. Cut back into clean, live wood, which you can identify by the pale green layer just under the bark.
- Branches crossing and rubbing on each other. The wound reopens every time the wind blows and never closes over.
- Suckers coming from below a graft union on a rose or a fruit tree. They belong to the rootstock and will outgrow the variety you paid for.
- All-green shoots reverting on a variegated shrub. They have more chlorophyll, grow faster, and will take the whole plant over if left.
Why fall is the wrong time for nearly everything
Autumn feels like the natural moment to cut things back, and for woody plants it is usually the worst window available. Pruning stimulates growth, and soft new shoots pushed out in September have no time to harden before the first hard frost kills them, which leaves damaged tissue behind on the plant. Autumn is also peak spore season for a lot of fungal disease, and a fresh cut is an open door. Herbaceous perennials are a different matter, and many of them are better left standing over winter anyway for the seedheads and the insects sheltering in the hollow stems.
Fruit splits along family lines
Apples and pears are pruned in the dormant season, roughly midwinter, when the leaves are off and the structure of the tree is visible. The tree's reserves are in the roots at that point, so it responds with vigorous growth in spring, which is what you want when you are building a framework.
Stone fruit is the opposite, and this is the exception that costs people trees. Cherries, plums, damsons, apricots and peaches are pruned in late spring or summer, in dry weather, while the tree is in active growth. The reason is disease: silver leaf and bacterial canker both infect through wounds and are most active in the cool wet months, while a tree in summer growth seals a cut quickly. If you only remember one date from this article, make it that one.
Where the cut goes
On a branch, cut just outside the branch collar, the slightly swollen ring of tissue where the branch meets the trunk. That collar contains the cells that grow over the wound. Cut flush to the trunk and you remove it, leaving a wound that stays open for years. Leave a long stub and it dies back and rots instead. Do not paint the cut with sealant either. Trees compartmentalize damage from the inside and a coating traps moisture against the wound rather than helping it.
- Twelve inches or so out from the trunk, saw upward from underneath until the blade starts to bind, roughly a quarter of the way through.
- Move an inch further out and cut down from the top. The limb falls, and the undercut stops the bark tearing a strip off the trunk as it goes.
- Now remove the remaining stub with a clean cut just outside the collar, supporting the weight with your free hand.
How much to take, and one thing you cannot undo
For an established tree, a quarter of the live canopy in one season is a sensible ceiling and less is usually better. Topping a tree, cutting the main leaders back to stubs, is not pruning: it triggers a mass of weakly attached watersprouts, opens large wounds that decay inward, and produces a worse-shaped, more hazardous tree than the one you started with. For an overgrown shrub, renewal pruning is gentler and works: take out a third of the oldest stems at ground level each year, and after three years you have replaced the whole plant without ever leaving a gap in the border.
Conifers come with a warning that catches people out on hedges. Most of them, including leyland cypress, spruce and pine, will not produce new shoots from bare old wood, so a hedge cut back past the green growth stays brown on that face permanently. Yew is the notable exception and regenerates readily from old wood, which is why it is worth the wait as a hedge. Check which one you have before the shears come out, because there is no version of this you can fix next season.