Checklist

If you're thinking of buying a line trimmer, here's what you need to consider.

Electric vs petrol

Petrol
Performance and portability are the two main advantages of petrol. All our petrol models performed better than the best of the mains-electric trimmers. Drawbacks are the hassles of mixing petrol and oil, yank-on-the-cord starting, louder noise, and expense.

Mains-electric
With one of these you don't have starting problems: just plug it in and pull the trigger. Drawbacks are the need to be within extension-lead distance of a power point and a performance that’s slightly lower than petrol models – although the top-mount mains-electric models performed quite respectably.

Cordless
Convenience is the selling point here. Drawbacks are low performance, having to remember to charge the battery, and restricted running time. These models are best suited to light tidying and edge-trimming.

Other things to consider

Starting
If you're keen on a petrol model, look for one with a clutch – these are generally easier to start.

Controls
Electric models usually just have one control: on/off.

Petrol models usually have 3 controls: the choke (for starting), the on/off switch; and the speed control trigger. Labelling on controls should always be clear and easy to read and follow. The on/off switch on a petrol trimmer is more convenient if it is on top of the shaft, rather than on the motor.

Some trimmers have "trigger interlock" buttons that add to safety by stopping accidental operation.

Shaft
There are two main type of petrol trimmer: curved shaft and straight shaft.

• Curved shaft trimmers are popular for home use. The curved shaft keeps the cutting head at the correct angle for attacking the grass. Power is delivered via a flexible cable inside the shaft. Some models have a clutch which operates automatically when the motor speeds up - this makes starting easier, and you can carry the trimmer safely when it's idling, without the head rotating.
• Straight shaft trimmers are more robust than curved shaft models, so are recommended if you want to do heavier work like cutting scrub or breaking in new ground. They have a gearbox at the head, which can take a cutting blade as well as the usual trimming head. The long shaft makes this type more comfortable to use, and better for dealing with a slope. However, they are more expensive, and heavier.

Balance and comfort
Trimming will be easier if the machine is well balanced and not too heavy. Before you buy, try the machine in both the horizontal and vertical cutting positions, to determine if you can realistically use it for long periods. We've found models with their motor at the bottom of the unit were more uncomfortable than those with top-mounted motors. They were also more awkward (heavier) to swing from side to side.

Longer models are generally more comfortable, especially for taller users. Short models are lighter, but an average-height user may have to stoop, which could cause back problems over a long period. A lighter machine is easier to carry, but lighter machines vibrate more and may be too flimsy to last well.

It's a very good idea to get a model with adjustable handles and shaft length. It's also worth considering a shoulder harness: they can take a lot of the weight off your hands and arms.

Feeding and replacing line
Most trimmers have a "bump line-feed system" to replace worn line. To feed out more line, you simply bump the cutting head on the ground. If too much line is fed out, it's automatically cut to length by a blade on the guard.

The other option is automatic line feeding, which means the line feeds out by itself. Our tests show these don't always work properly under all conditions. We think a semi-automatic (bump-on-the-ground) line feeder is a better bet.

Safety features
Your trimmer should have a safety guard that covers as much as possible of the cutting swath without preventing you from seeing what's happening. It should also have a fixed blade or post that automatically trims the line to a maximum length.

Re-spooling
Loading new line onto the spool can be the most difficult part of using a line trimmer. Single-line heads are easier to re-load, but they don't cut as well as twin-line heads.

The Littl' Juey line trimmer has an unusual head design that makes its manual loading easy. It can be reloaded in a few seconds rather than the minutes it takes some other models. Littl' Juey also sells this head separately – so it can be attached to other makes of trimmer. See What we found for more information.

Edging
This requires more skill than normal trimming. To work along a path, you have to turn the machine 90° (so that the head is vertical and just above the ground) and keep to a straight line. For edging, the handle should be easy to rotate and lock on to the shaft. To maintain a straight edge, you should have a clear view of the cutting line beyond the safety guard. An edging guide is a useful feature. This helps you to keep the trimmer a fixed distance from a vertical surface such as a fence. Some trimmers use a roller instead.

Motor power
Don't be misled – motor power is not a reliable guide to cutting ability.