How we test hedge trimmers
By Adele Dyer
Which? tests hedge trimmers on deciduous, evergreen and conifer hedges to find the best ones for keeping your garden looking neat.
We've tested a wide range of hedge trimmers over the years, covering big-name brands including Black & Decker, Bosch and Stihl. Our expert testing guide explains what we look for in a hedge trimmer and what makes a Best Buy.
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Why our hedge trimmer tests are different
Hedge trimmers take the hard work out of keeping your hedges looking neat, and a well-cut hedge will make the whole garden look better. We carry out independent, scientific tests designed to discover how well hedge trimmers cope with challenging hedges and whether they leave them looking crisp and neat or chewed and ragged.
Our reviews show whether or not a hedge trimmer can cut a variety of hedge types. We also pay attention to the speed of a hedge trimmer, ease of use and safety features.
What are Which? Best Buys and Don't Buys?
Best Buys are given to hedge trimmers that impress the most in our rigorous tests. An electric hedge trimmer that scores over 74% is a Best Buy. Petrol hedge trimmers must score over 76% and cordless hedge trimmers must score over 80% to be a Best Buy.
How is the Which? score calculated?
Each of our hedge trimmer assessments make up part of the overall test score, which is a percentage figure we award to each model. Some assessments are more important than others and so carry different weights.
As electric, cordless and petrol hedge trimmers have different strengths and weaknesses, we adjust our test weightings accordingly.
Key question: how well does the hedge trimmer cut a variety of hedge types?
There are many shrubs that can be cut to form a hedge. Some, such as cherry laurel, have tough stems and leathery leaves. Others, such as privet, have thin, whippy stems and soft leaves. A good hedge trimmer should be able to cut through all types of growth, and we've developed our tests so that we now cut the most common types of hedge.
Over the past few years we've asked more of the hedge trimmers we test. In 2012, we cut only conifer hedges. In 2013, we added deciduous hedges, and in 2015, we also cut laurel hedges. The deciduous hedges in 2013 were blackthorn and hawthorn, while we swapped to privet in 2015, as this is such a widely grown hedge.
Our three testers each cut at least 10m2 of each hedge type with each hedge trimmer to see how well they cut, how quickly they cut and how easy they are to use.
Not all hedge trimmers leave a neat finish. Some don't make a clean cut but rip through stems, leaving long 'tails' that make the whole hedge look untidy. Some don't cut neatly through leaves, but chew them up, again leading to messy-looking hedges.
Key question: how quickly will the hedge trimmer cut?
Our testers cut at least 10m2 of conifer, deciduous and evergreen hedges and time how long it takes to cut this amount of hedge. We changed the way we test in 2018 and now cut at least 20m2.
The times are then averaged to make sure the time taken is representative of each hedge trimmer's performance and isn't affected by the user cutting through a particularly tough or gappy section of hedge.
Key question: is the hedge trimmer easy to set up and use for the first time?
Three testers assess each hedge trimmer for ease of use, taking into account how easy they would be for an older or less able gardener to operate.
We rate the machines on 18 criteria, including how easy they are to carry around, how comfortable the handles and switches are, how simple they are to use for vertical or horizontal cutting and whether noise, vibration, weight or balance are a problem.
Key question: how much hedge can I cut with a cordless hedge trimmer?
Battery technology is improving rapidly and cordless hedge trimmers save the hassle of trailing leads on electric models and the weight and noise of a petrol hedge trimmer.
We cut the same three hedge types as with electric and petrol models, but rather than stopping after 10m2, we carry on until the battery has been exhausted. We note how many minutes this is and calculate how many metres of hedge we've cut in this time, and how well the trimmers have cut.We rate how easy the battery is to remove and refit, and time how long it takes for the battery to recharge.
Key question: is the hedge trimmer designed in such a way that it's impossible to injure yourself in normal use?
We check hedge trimmers for electrical and mechanical safety. Features we look for include:
- Two separate switches so you have to keep both hands on the machine.
- Blades that stop the instant you release one of the switches, so touching a still-moving blade is impossible.
- Blade extensions – fixed teeth that extend well beyond the cutting teeth, so you can’t do serious damage if you accidentally brush the trimmer against your leg.
Over the 30 years we’ve been testing hedge trimmers, safety features have improved considerably. In the early days we campaigned to improve safety features and these have now been incorporated into international standards and adopted by all manufacturers.
Pick the perfect hedge trimmer with Which? reviews
As you can see from our testing table below, there is a wide variety in the scores of hedge trimmers in the same price bracket.
Browse all our hedge trimmer reviews to find your perfect model.
Is the battery replaceable?
Lithium-ion batteries always deplete and eventually die over time, and at Which?, we believe that cordless products should last longer than the batteries they come with. That's why we no longer give cordless hedge trimmers Best Buys if spare batteries cannot be bought from the manufacturer – no matter how good the hedge trimmer might be.