String trimmers, or weed whackers as they are more casually known, are a friend to the time-short gardener. These handy garden hackers use a rapidly spinning piece of string to cut through the plants, rendering them down to shreds that you can either leave as ground cover or throw into the compost. They are faster than a rake or spade and more controllable than lawnmowers, allowing you to, with a bit of care, clear out weeds around larger plants or interlopers in your flower beds.
Because they use a spinning piece of nylon string, they won’t scrape the woodwork on your fence or dig up the earth, but they will cut through anything with a stem under a half-inch or so thick. All of the strimmers we tested did have a tendency to throw small bits of rock or sticks around as they worked, although they included safety guards that kept this away from the operator. So, they should always be used with caution, with appropriate safety equipment, and kept away from pets and children.
And, if you're looking to master your land's turf as well as the edges, be sure to dip into T3's best cordless lawn mower, best robot lawn mower and best petrol lawn mower buying guides, as they are stuffed with top-rated sward slayers.
Finally, if you need to tame a horrific hedge then a quick look at T3's best hedge trimmers article will help you select the best tool: it's stuffed with quality corded and cordless systems.
Choosing a String Trimmer
There are three things that you need to decide before you choose a string trimmer: price, power, and size.
The models we tested range from about $40 for an entry-level corded model (the Black & Decker BEST935) to $300 for the largest cordless electric model (the DeWalt DCST972X1). That’s a wide range, but the bottom line is that corded ones are cheaper, and the bigger the cutting width, the more expensive the string trimmer is.
Most of the models that we tested are electric. All but the very cheapest of these use clip-on batteries for a cordless trimming experience and offer between 20 and 45 minutes of plant whacking time from a single charge. That's enough for a light trim on a smaller yard, but bigger or more overgrown yards may require multiple batteries or one of the gas-powered models that we also tested, which will run for as long as you have gas to put in them.
Finally, there is the cutting width, a measure of how wide the path that the string trimmer can cut through is. This ranges from 13 inches up to 17 inches. The bigger the width, the quicker you can deal with larger areas of weeds and unwanted vegetation. However, string trimmers with wider cutting widths are larger and can be more awkward to handle. For most small yards where you just want to trim weeds in the beds and the edges of the lawn, a 13-inch model is fine. For larger yards and areas with lots of flower beds and lawn edges, a 15 or 17-inch model will make for quicker work.
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The Ego Power+ ST1521S is a big string trimmer any way you look at it, with a 10-pound weight, height of over five feet, and a wide 15-inch cutting path. Although it is big and heavy, it is surprisingly easy to handle, as the weight is well balanced between the battery at one end and the motor on the other. It does tend to weigh you down with extended use, though. The tube is carbon fiber, which is lighter than metal and keeps the weight at the ends for better balance.
We found it easy to trim weeds with, with light touch control that is sensitive and responsive. We had no issues with string tangles: the ST1521S spooled out extra line when we tapped the head on the ground without issues through our tests.
It also includes a unique line loading system, called Powerload. With this, you feed the loose line through the head, then press a button and the motor slowly reverses to load the cutting line onto the spool, ready to use. It is a bit awkward (as it still involves loading 19 feet of loose line), but it is easier to load than fiddling with a spool of line.
Priced at about $220, there is a lot to like in this string trimmer. It cuts well, is easy to use and has plenty of cutting power. Our only real complaint is that you can’t fold the tube in half for easier storage, as it is rather large.
The DeWalt DCST972X1 is a great heavy-duty rechargeable string trimmer, but it is also the heart of a whole system. Two things about it are swappable: the batteries and the tool on the end.
The DCST972X1 uses DeWalt’s own FLEXVOLT battery system, which means that the included battery can be used with a wide range of DeWalt's other tools, from power drills to demolition hammers. While you might not need a demolition hammer at the moment, having batteries that can be used across devices can save you a lot of money if you are buying other power tools. As long as they are from DeWalt, that is: they aren’t compatible with other manufacturers' tools.
The other thing that can be swapped out is the tool on the other end. You can get additional powerheads that do things such as cut limbs, blow leaves or cut heavier brush. Again, that’s a big plus if you need these extra tools.
As a string trimmer, the DCST972X1 is excellent: we found that the wide 17-inch trim path meant it could cut through patches of weed in record time, and it had the power to handle everything but woody stems. The included 4 Ah battery lasted for about 35 minutes of trimming, which is enough to get through a lot of weeds.
The Husqvarna 220 iL has a trick up its sleeve: the spinning head can rotate both ways, so it can cut to the left and right. That’s a neat and surprisingly useful trick, as it means that you can more easily cut up against fences and into tight spots without having to flip the trimmer over.
The 220iL is also a light, easy to maneuver string trimmer with two power levels for cutting light or heavy foliage. Even the lower level is quite powerful, slicing through all of the weeds in our tests except a heavier weed with a woody stalk that required several passes to get through. The manual string loading system is also a bit of a pain: you push the line through the head, then turn the cover of the spool to wind the string onto the spool. With 20-odd feet of string, that takes quite a lot of winding.
The Worx WG170.2 is one of the smaller and more affordable string trimmers that we tested, with a 12-inch cutting width. That means it took some time to work through a larger patch of weeds, but the smaller, lighter trimmer was easier to use on light tasks like edge trimming and weeding in a flower bed.
It also comes with one neat accessory: a clip-on wheel that holds the trimmer at a certain height, so it can double as a lawnmower. Although it doesn’t have as much cutting power as the others, it would be perfect for a smaller yard where the bigger models were too much.
Ever go partway through cutting weeds only to realize that your cell phone was out of juice? The Greenworks 24V has you covered: the PowerAll 24V battery that drives it has a USB port on it, so you can charge up your phone with a standard USB cable. You can’t do that while trimming the lawn, though.
The Greenworks 24V is a decent string trimmer overall. It cut pretty well, although it did struggle with some of the larger weeds that we tested it on, either not cutting them or taking multiple passes to get through. It had plenty of power to trim smaller weeds and edge the lawn, though, and the 13-inch cutting width is fine for most uses. So, it would be a good pick for a smaller yard or lawn that just needed a trim at the edges.
Priced at about $40, the Black & Decker BEST935 is the cheapest of the string trimmer we looked at, because it doesn’t have a battery. Instead, it runs from a power cable that you supply. This does mean that you need to watch where you are trimming: it isn’t likely to cut through a power cable, but it could damage it. A cord lock that holds the cable in place on the trimmer prevents you from inadvertently pulling the power cable out by going too far, but you aren’t going any further than your cable.
The Black & Decker BEST935 is a decent trimmer, with a moderate amount of cutting power. It lacks the fancy features of the more expensive models: you load a new line by putting a new pre-would spool into the head of the trimmer, there is only limited control over the power of the motor and it balked at cutting anything with a stem more than a quarter-inch or so thick. But if you are just trimming lawn edges and the odd weed in the flower bed, it might be all that you need.
If you are clearing a larger area (or like helping your neighbors out), you’ll need a trimmer that can keep going and going. All of the portable electric trimmers can only last about 30 to 45 minutes, after which you need to stop and recharge the battery. With a gas-driven model like the Husqvarna 330LK, you just stop and fill up the tank when it runs out: quick and easy.
This model also has some decent cutting power: the two-stroke 1hp engine drives the spinning head directly, so it can quickly speed up and slow down as required. Plus the wide 20-inch cutting width means that it can cover large areas with speed.
The downside is that, well, gas engines are noisy and dirty. Sorry, gearheads, but it is true, especially when you are carrying the motor around with you. It is a two-stroke engine, so you also have to mix two-stroke oil in with the gas before you use it with a 50:1 ratio. That means you can’t just put it into the car after you are done: it will gunk up your engine.
The Worx WG163 is one of a few two-in-one tools on our list, acting as a grass trimmer and wheeled edger in one. Worx promises quick, hassle-free conversion between the modes and a handy auto line feed, both of which mean you won’t get slowed down mid-landscaping.
The company includes two li-ion batteries into the bargain, so you can keep using one while the other recharges. A 90-degree pivoting head also makes it easier to trim tricky spots, so if you have lawn furniture, a trampoline, or a tricky-shaped garden, it may be a good buy.
You can see how this strimmer stacks up to our number one choice in T3's Terratek 20V vs Worx WG163 comparison feature.
This high-end model features a double-line spool which is more efficient than a single line, obviously. The jury’s out on how long before something goes awry with the spooling system but it looks robust enough and, we hope, reliable.
The FSA 57’s 11-inch cutting diameter is perfect for larger lawns but you’d be better served with the larger and longer-lasting AK 20 battery (40 minutes) rather than the AK 10, which lasts for about 20 minutes.
The FSA 57 features a length-adjustable shaft, an adjustable loop handle and a comfy trigger grip that feels secure in the hand. This grass trimmer is heavier than some others and you will likely feel like you’ve done a workout after several minutes of using it but, hey, it trims superbly well and, given Stihl’s rosy reliability record, it’s likely to go on running longer than most.
This trimmer is powered by a 2.0Ah lithium-ion battery that delivers about 24 minutes of operation before needing to be recharged – that’s more than enough time for any small to medium size garden. Naturally, though, if you have a very large garden then expect to buy additional batteries or wait for a recharge.
The cutting path of the Ryobi strimmer is 10 inches, which is about average. However, the lower hand grip isn’t adjustable like other models so you might find it’s not as comfortable to use if you’re short in stature. On the plus side, it does feel light in the hand.
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What You Need to Know About String Trimmers
These string trimmers are designed for trimming back small and medium-sized weeds: they won’t work on anything with a stem thicker than a half-inch or so. For that, you’ll need a chainsaw or a brush trimmer, both of which are designed to cut through much thicker vegetation.
The most popular power source for these devices is a rechargeable battery. All of the string trimmers come with a charger and a single battery, but it might be worth investing in a second battery if you have a larger yard or more weeds to trim. If you already have a rechargeable garden tool from one manufacturer, you might also be able to share batteries: all of the devices from Ego, for instance, use the same style of battery, so you can swap and share them between devices. That isn’t the case between manufacturers, though: you can’t use a DeWalt battery with a Greenworks trimmer, for instance.
One of the string trimmers we tested uses a power cord. For this, you will need one that is as long as possible, but which can also handle enough juice to run the string trimmer, which can draw a lot of juice. Check the manual for specifics, but you should get one that is designed for outdoor use and is rated for at least 12 Amps.
Some string trimmers are powered by gas. For these, you can use regular gasoline, but make sure that you get an appropriate container to store it in. The tanks on these usually hold about half a gallon and use two-stroke engines, which require a mix of gas and oil to run and lubricate the motor. They don’t usually come with the appropriate oil, so make sure you pick up some of that as well. Once you have mixed the oil into the gas, write on the container so you don’t accidentally put it in your car, and give it a good shake before you fuel up the trimmer.
You should always use safety gear with these string trimmers, including goggles and long pants. Although they do include safety covers that stop stones or sticks from being thrown into your face, they can knock these into the face of those around you or even over a fence, so be careful to stay safe and use them appropriately.