May is the month in which the garden reaches its maximum spring splendor. The temperatures stabilize, the light increases and the plants enter the full vegetative phase: it is the moment in which the sap flows with more force, the buds explode and the flowers color balconies and gardens. Precisely for this reason, May is also one of the months in which it is easier to make pruning mistakes – often with consequences that are only seen weeks later, when it is too late.
The general principle to keep in mind is simple: plants that flower on the previous year’s branches should not be pruned, because the cuts would eliminate the flowers that have already formed. Likewise, interventions on species in full vegetative activity should be avoided, where an open wound favors sap losses, water stress and the entry of fungal diseases.
(Read also: Which shrubs and trees you should NOT prune in April)
Shrubs
Among the shrubs not to be pruned in May we highlight:
All these shrubs have one fundamental characteristic in common: they produce their flowers on the branches that grew during the previous season. Pruning them now means directly eliminating the buds or flowers already present, compromising the flowering of the entire season. The correct intervention should be carried out immediately after flowering, when the plant still has time to form new branches that will flower the following year.
Climbing plants
Even climbing plants, which give their best in late spring, should not be pruned in May; among these we find:
Wisteria in particular is a species on which mistakes are often made: it flowers on the lateral spurs developed on old branches, and a cut at this moment destroys months’ work. Even for climbing roses, which give their best in May, it is preferable to wait for the end of flowering before intervening with scissors or shears.
Trees
Even if May is the month to dedicate to pruning some fruit trees, simply removing the driest branches, there are other species that should not be touched. We are talking about:
The cherry tree, for example, is very vulnerable to fungal diseases such as moniliosis and cytopor: any cutting done out of season opens a gateway to these pathogens. Eucalyptus in full spring growth reacts badly to pruning, with the risk of sunstroke on open wounds. The horse chestnut, together with maple, birch and walnut, is instead subject to the so-called “weeping”: in this period the sap flows with such pressure that a cut wound can leak liquid for weeks, significantly weakening the plant.
What to do in the garden in May instead
While the scissors must be kept at rest for many species, May still offers a lot to do. It is the ideal time for deadheading, that is, the removal of withered flowers on herbaceous plants and roses, which stimulates the production of new buds without affecting the structure of the plant. You can take the opportunity to fertilize with slow release products, water regularly as the temperatures rise, and arrange braces and supports for the fully growing climbers.
How to understand if a plant blooms on old or new branches
To avoid making mistakes, just observe when flowering appears. If the plant flowers in spring, before the new shoots have had time to develop completely, it almost certainly does so on the branches formed the previous year: in this case pruning should be postponed until after flowering. If, however, the plant blooms in summer or autumn, the flowers will form on the new branches of the current year, and early winter or spring pruning is the correct one. If in doubt, it is always better to wait: a pruning delayed by a few weeks does much less damage than one carried out at the wrong time.
You might be interested in:
