• A cordless string trimmer can be used anywhere in a landscape.soldier edging grass image by Daria Miroshnikova from Fotolia.com
  
  String trimmers are indispensable garden tools used to trim grass and weeds, particularly around edges or objects. String trimmers are also called weed whackers and line trimmers. They trim grass by using a plastic string mounted in a rotating head that spins at a very fast rate. The following trimmers are listed by ConsumerSearch.com, which draws from ratings on a range of sites. Selecting the best-rated string trimmer depends on what your needs are.
  
  

Cordless Electric Trimmer

• Cordless electric trimmers are a good choice if you don't have a large area to trim. They are lightweight and economical. The best rated cordless electric trimmer is the Grass Hog NST2018 from Black and Decker. This is a quiet trimmer, though not a good choice if you have tall weeds or grass. Batteries last up to an hour per charge.
  
  

Corded Electric Trimmer

• Corded electric trimmers have a built-in disadvantage: you have to deal with the extension cord. But there are advantages. Corded electric trimmers are quieter, lighter and easier to use than most gas models, they're low-polluting and they handle overgrown weeds and grass just as well. The best rated corded electric trimmer is Stihl FSE 60, which is reported to handle tall grass well.
  
  

Gas Trimmer

• Gas string trimmers offer the advantage of a more powerful tool, but they are often heavy and difficult to use. Another disadvantage is the necessity of mixing gas and oil. If you don't mind the gas/oil mix or a heavy tool, a gas trimmer can handle tough jobs. The best rated gas trimmer is the 29 cc, four-cycle Craftsman 79194, which doesn't require mixing oil with the gas. Two-cycle gas trimmers are usually easier to start and require less maintenance than four-cycle trimmers. The SRM-225 from Echo is the two-cycle trimmer with the best ratings.
  
  

Propane Trimmer

• Propane string trimmers have as much power as gas trimmers, and they are more eco-friendly. Propane trimmers allow you to forget about mixing gas and oil, but you have to stock up on canisters. The best-rated propane trimmer is the Lehr Eco Trimmer ST025DC. It is lighter than a gas trimmer but heavier than a lot of electric trimmers. One disadvantage to this type of trimmer is that you have to find a retailer that carries the propane canisters.