Why Pruning in August Is Different
Unlike the aggressive pruning of late winter, which encourages vigorous new growth, August pruning is about maintenance and preparation. By this time of year, most plants are slowing down their growth as they prepare for autumn. Pruning now is less about stimulating
a burst of new foliage and more about improving the plant’s health, managing its size, and in some cases, encouraging a better bloom or fruit yield next year. Incorrectly pruning in late summer can risk snipping off next year's flower buds or promoting tender new growth that won't have time to harden before the first frost. This makes it crucial to identify your plant before you make a single cut.
Plants That Welcome an August Trim
Certain plants respond very well to attention this month. Rambling roses that have finished their main flush of flowering can be pruned now to keep them in check and promote healthy structure. Similarly, climbing plants like Wisteria benefit from a summer prune to control their vigorous growth and encourage the development of flowering spurs. It is also an ideal time for stone fruit trees such as cherries, plums, and apricots. Pruning these trees right after you have harvested the fruit helps to manage their size and allows the wounds to heal quickly in the dry, warm weather, reducing the risk of disease. Summer-flowering shrubs like Lavender and Hebe can be given a light trim after their flowers have faded to keep them compact and tidy.
The 'Do Not Prune' List for Late Summer
Just as important as knowing what to prune is knowing what to leave alone. The cardinal rule is to avoid pruning spring-flowering shrubs. Plants like Forsythia, Rhododendrons, Azaleas, and Lilacs have already formed the flower buds for next year's display on what is called 'old wood'. Pruning them now means you will be cutting off all of next spring's flowers. The proper time to prune these is immediately after they finish blooming in the spring. You should also generally avoid pruning trees that are known to 'bleed' a lot of sap when cut, such as maples and birches, as the sap flow is still active. Waiting until they are fully dormant in winter is a much safer bet.
A Special Case: Hedges and Apples
August is often the last call for trimming hedges before the weather turns cold. Giving them a final trim now will ensure they look neat through the winter, as their growth will slow significantly. For trained apple and pear trees, such as espaliers and cordons, summer pruning is essential. This process involves cutting back the current season’s growth to encourage the development of fruit-bearing spurs rather than leafy shoots. However, for standard, untrained apple trees, major structural pruning is best left for the dormant winter season. Light thinning of crowded growth can be done, but avoid any heavy-handed cuts.
Best Practices for August Pruning
Regardless of the plant, always follow a few basic rules for the best results. First, ensure your tools—be it secateurs, loppers, or a pruning saw—are sharp and clean. This makes for cleaner cuts that heal faster and reduces the chance of spreading disease between plants. Second, never remove more than a third of the plant's mass at once. The goal of August pruning is refinement, not a complete overhaul. Focus on removing any dead, damaged, or diseased wood first. Then, look for branches that are crossing or rubbing against each other, as this can create wounds and lead to future problems. Finally, step back frequently to assess the overall shape and ensure you are achieving a balanced, natural look.
