String trimmers have either a straight shaft or a curved shaft, the latter of which is bent about halfway between the handle and the spinning trimmer head. A straight shaft is often better for taller users because it’s longer, and the design lets you trim without kneeling or bending to keep the trimmer head close to the ground.

Shorter users may prefer a curved shaft because it’s a little easier to hold and maneuver, and its design makes it more convenient to keep the cutting head perpendicular to the ground. If you’ve never used a string trimmer, try one of each at a home center or hardware store to see which feels more natural.

Power Source
A string trimmer can be powered by gasoline, by a battery, or with a traditional power cord plugged into an outdoor outlet. In our tests we find that all three types can cut well, depending on the model.

Corded electrics are the cheapest but only a good option if you have an outdoor outlet and a long extension cord—you’ll rarely find an outdoor cord longer than 100 feet, so if you need to trim an area more than 100 feet from an outlet, choose another type.

Battery-powered models often cut as well as gas, start instantly, and run quietly. If you have a battery-powered lawn mower, the smart move is to buy a string trimmer from the same brand because you’ll be able to use the batteries interchangeably and always have one fully charged. Otherwise, expect to trim for about 30 minutes on a single charge.

Gas-powered string trimmers are the most common. They’re loud, so you’ll need hearing protection, but they can go anywhere and run indefinitely, provided you keep adding fuel. Models with a four-cycle engine run on regular gasoline, but be sure to add fuel stabilizer to the gas before prolonged storage—the ethanol in gas can gum up the engine, making it difficult to start.

Two-cycle models are cheaper than most four-cycle models, but they emit more pollutants and require you to mix gas and oil in specific proportions, usually 40:1 or 50:1, before adding fuel to the tank. You can also buy cans of premixed gas and oil for string trimmers (and other outdoor power equipment) at the home center. It costs more than mixing fuel yourself, but a single $7 can is likely to last an entire season.

Should You Buy a Powered Base?
With both gas- and battery-powered string trimmers, you’ll have the option of buying a stand-alone tool or a powered base. The latter is basically an engine or a motor designed to accept different attachments, and it’s typically sold with a string trimmer head. For most models, you can also get a hedge trimmer, pole saw, edger, and brush cutter, and even a cultivator attachment. It’s a good option if you need a string trimmer and any or all of the additional tools, and you don’t have the space for multiple tools, or the money, to buy each separately.

Mind the Gap
Before you buy any string trimmer, look at the cutting head, where it meets the shaft of the trimmer. If there’s a large gap, be warned that tall grass will probably get wrapped around the shaft in that spot. Instead, look for a model with a minimal gap, or one with an easy-to-remove cutting head, so you can quickly pop the head off and get rid of weeds. 

Safety First
String trimmers can easily break through skin and send debris flying while they cut. They have a shield to deflect most debris, but even so, you’ll want to wear gloves, protective eyewear, boots, and long pants, in addition to hearing protection for gas models.