Monty Don has advised gardeners that now is the perfect time to trim hedges, as the nesting season for robins and other garden birds has ended. In a 2024 blog post, he explained that hedge trimming is now fully safe to carry out because "the vast majority of nesting birds have fledged" in the transition between summer and autumn.
Why timing matters for birds and plants
Gardeners should not be afraid of disturbing active nests, which is strictly off-limits during the official bird nesting season from March to August. But there is another reason to start before autumn sets in: those who prune at the end of summer can expect "results in slower, less vigorous regrowth than a winter trim."
In simpler terms, the shape you cut now is more likely to hold through the colder months, rather than the fresh unwanted growth resulting from cuts later in the year. Trimming too early, such as in the height of summer, can also cause problems, with plants more likely to suffer from heat stress compared to those trimmed in the cooler days of late September and early October.
Technique for a clean, safe cut
Before starting the job, Monty stresses it is essential to double-check inside the denser parts of the hedge for any late nesters left over from the height of summer. He suggests starting with the sides of the hedge to achieve a slight "batter," or outward slope from top to bottom. This prevents the lower section from being shaded out by bushier top growth, distributing sunlight more evenly for a denser plant overall, or as Monty describes it, "fully 'furnished' right down to the ground."
Once the sides are done, move to the top, using a length of string stretched between two canes as a simple and reliable guide to keep the cut level. Don't go overboard, though—light shaping and general neatening should be the goal for this month. Harsher cuts should be left for next year, since they can trigger soft new growth that is unlikely to survive frost damage.
After the trimming
After trimming, Monty notes it is worth mowing up the resulting trimmings and adding them straight to the compost heap. Evergreen clippings should be directed to local councils' green waste.
