Mechanical Grass Trimmers

Shears

• Lithium-ion rechargeable batteries power many hand-held grass shears, and hand-held grass shears powered by nickel cadmium batteries are on the market, too. Some models are rotatable for right- or left-handed users, and some shears can be equipped with long handles so you don't have to stoop or bend to trim grass. Grass shears are meant for use in small areas that need precise trimming. Using shears helps to prevent cutting the grass too closely to its roots.

Electric String Trimmers

• Electric trimmers are generally lighter in weight -- about 5 pounds -- and less powerful than gas-powered models. They are best suited for small properties because their range is limited due to length of extension cords need to connect them to electrical outlets. The trimmers have a nylon line that spins in a circle underneath a protective cover. The line is strong enough to sever grass, but the line wears and has to be advanced as cutting proceeds. That procedure varies by model. Various diameters of line are available to suit the trimming job. Electric trimmers should not be operated during rain or where electrical connections might encounter moisture. Protective clothing and eye wear should be used with all string trimmers.

Gasoline-Powered String Trimmers

• Gasoline string trimmers are heavier -- from 9 to 14 pounds - than electric string trimmers because they incorporate a gasoline engine to power the cutting mechanism. They can perform more difficult jobs than most electric models. Gasoline trimmers are noisier and bulkier than electric trimmers, and they are restricted in some areas, such as California, because of the air pollutants they produce. Four-cycle trimmers produce less pollution than two-cycle trimmers. Non-electric trimmers produce at least 85 decibels of noise, a level that requires ear protection for safety. Gasoline engines need regular maintenance.

Battery-Powered Trimmers

• Rechargeable batteries power cordless trimmers. Although more mobile than electric trimmers, they are less powerful, and their battery charge doesn't last long. Some models have a 30- to 40-minute battery charge after five to seven hours of charging. Rechargeable trimmers are less noisy than gasoline-powered trimmers, simple to start and use and emit no fuel pollutants.

Propane-Powered Trimmers

• Propane-powered trimmers are considered environmentally friendly because they produce far fewer emissions than gasoline trimmers, reducing particulates released by 97 percent and carcinogens by 96 percent. Propane is supplied in non-refillable 16.4-ounce, stainless steel canisters that provide about two hours of operating time. Four-stroke string trimmers are among the models available. Propane-powered trimmers are comparable in price and cutting power to gasoline-powered trimmers, but they are less noisy, less polluting and easier to maintain. Their operating costs, however, are higher than those of gasoline trimmers.

Edgers

• Edgers are used to trim grass that grows against sidewalks and driveways. Power edgers rather than hand edgers are most useful if a yard has lots of edges to maintain and/or has tough, aggressive grass such as Bermuda grass. Edgers have an adjustable-height wheel with a sharp cutting edge. Gasoline-powered edgers are most common, but electric edgers also are available. Electric models are not as powerful as gasoline models, which are mostly meant for commercial use or the maintenance of large areas. Some string trimmers have a rotating head for edging or an edging attachment.