Think Twice Before You Prune These Plants in June – You Could Sacrifice This Year's Flowers and Next Year's Growth
Improper pruning can be fatal in early summer for some trees
As the garden really starts to fill up in June, there can be an urge to cut things back in an attempt to wrestle back control. While there are shrubs, perennials, and hedges that will benefit from a trim now, others won’t. Here are some plants to never prune in June, and why.
Summer bloomers rank high on the plants not to prune this month, for the simple reason that you’ll lose flowers. Add to that, some gardeners might not want to prune shrubs that flower in spring, as missing the boat means you’ll affect next year’s display. The consequences of improper pruning can stretch further than no blooms, though, as oak and elm trees are at risk of fatal diseases if they are pruned this month.
Knowing the right plants to prune in June ensures your garden remains beautiful and healthy. And understanding what not to prune in summer prevents missing out on flowers or unnecessarily putting trees at risk. Let’s take a look at four groups of plants to never prune in June, and see how many feature in your yard.
1. Summer-Blooming Plants
This one will just make sense to any gardener, but it warrants mentioning just in case. I know I might be teaching you to suck eggs, but there is no wisdom in pruning shrubs that burst into show in summer.
Any flowering shrub that naturally produces its flowers in summer will have spent many months forming buds and developing growth all in anticipation of blossoming. Why let them go through all that, only to prune them back before they’ve put on a show?
Any pruning this month will inhibit the display of flowers. You’ll merely remove flower buds – so don’t do it. This guidance covers panicle hydrangea, butterfly bush, rose of Sharon, crepe myrtle, hibiscus, smoke bush, potentilla, bluebeard, and many more.
If in doubt, remember the general rule of thumb that any plants that bloom from June onwards should be pruned in late winter or early spring, and not in summer. If it flowers before June, prune it after flowering.
It is not just shrubs that this applies to; the pruning guidance also covers perennial plants and flowering climbers that bloom in summer, like clematis, honeysuckle, passionflower, and star jasmine. These are all plants to never prune in June, too.
2. Trees at Risk of Disease
Losing flowers is bad enough, but there are some pruning mistakes you can potentially make this month that can have much more serious consequences.
One such error to avoid is pruning oak trees; these statuesque beauties should NEVER be pruned in June. If you trim an oak in early summer, the tree will bleed sap and attract pests that can carry oak wilt (Ceratocystis fagacearum).
The devastating fungal disease can quickly kill trees, potentially within months. It is a serious issue across the US, and it affects almost all types of oak. Only ever prune oaks during their dormancy, when the beetles that carry the fungus aren’t active.
The same guidance applies to pruning elm trees. The elm bark beetle carries the fatal Dutch elm disease, which is responsible for the death of millions of elms in Europe and North America. These beetles are attracted to the pruning cuts when active in spring and summer.
You should only ever prune elms in winter. Indeed, some states have restrictions on when elms can be trimmed. These are put in place to protect tree populations, so check any regulations for where you live.
Finally, trees at risk of the bacterial disease fireblight should not be pruned in early summer. That includes crabapples, mountain ash, and hawthorns.
3. Spring-Flowering Shrubs
This one isn’t a one-size-fits-all warning. Indeed, spring-flowering shrubs will only be plants to never prune in June if you live in warmer climates, while gardeners in colder zones may actually need to trim early this month.
We’re talking about the likes of rhododendron, azalea, forsythia, lilac, weigela, viburnum, and camellia. And it all comes down to when your spring-flowering shrubs bloom.
All these plants want to be pruned right after they finish flowering, as they start developing next year’s buds quickly after this year’s blooms end. If you wait too long to head out with the pruning tools, you can all too easily cut off next year’s buds.
If your shrubs are only just coming to the end of their show, then go ahead and prune – but be prompt about it.
If yours finished earlier in the spring, certainly anything more than a few weeks ago, it might be better to leave trimming for this year rather than depleting next spring’s display.
Prune if you might, but accept you’ll get fewer flowers – you have been warned.
4. Trees Vulnerable to Sap Loss
There are some trees known as ‘bleeder trees’ for their tendency to lose lots of sap when they are pruned. This list includes maples, birches, and walnuts.
In early summer, these trees have high sap pressure and will bleed large amounts of sap if they are pruned this month. While losing sap won’t necessarily kill a tree, it does weaken it and leave it more susceptible to pests and diseases.
If you wonder when to prune trees that are known to bleed lots of sap, the best course of action is to trim them in mid-to-late summer, when the sap flow isn’t as high.
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Let’s turn things around to end with. Rather than telling you what not to do this month, let’s look at what you can do in June.
The good news is that there is a lot you can plant in June, including fast-growing annual flowers, biennials to bloom next year, quick crops for summer pickings, and vegetables you’ll be harvesting in winter.
It really is a rich month for transforming flower beds and vegetable gardens, so why not get out, take advantage of the good weather, and get planting?
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