Operating manual: With a combo chipper/shredder, you drop branches into a chute, where they are chopped into chips by steel blades. At the top of the machine is a bucket for leaves and twigs, which are shredded with quickly rotating hinged steel blades. Some models have screens below the shredder that filter the leaves and send big pieces back to the shredder. Trash bags or cans can be attached to collect the shredded material.
Stand-alone chippers and shredders operate the same way. But instead of steel blades, some leaf shredders use plastic "blades" - strings that slide into a holder and chop up the leaves through high-speed rotation.
The drawback: Plastic blades need to be replaced more frequently, and they don't do as good a job with wet leaves, which often clog the mechanism and have to be dislodged. The advantage: Besides being inexpensive, plastic blades simply sting if you forget to shut off the machine before sticking your hand in to clear it - which, by the way, you should not do.
Power play: Gas-powered models are more powerful, and tend to be very noisy, and, of course, polluting. But they are more mobile than lighter-weight electric models, which can be operated only about 100 feet away from the power source using an outdoor Underwriters Laboratory L-rated extension cord. Electric cords can be sliced accidentally, so you'll need to be careful.
Peak performance: Engine horsepower and shredder revolutions per minute determine performance; the typical electric unit has a 1-horsepower engine. In addition, the efficiency of the machine is measured by chipper and shredder blades - the more the better.
Smaller, generally less-expensive chippers operate by direct drive - the blades move whenever the motor is in operation. Bigger, more expensive models have clutches that disengage the blades so they stop rotating even when the motor is running.
Size matters: Don't expect even a 10-horsepower gas chipper/shredder, the most powerful on the market, to chop anything larger than branches about three inches in diameter. Thicker branches must be split into more bite-size pieces first.
Jargon alert: Manufacturers refer to "reduction ratio." If a shredder has a ratio of 20 to 1, for example, it means 20 bags of leaves will become one bag of mulch when processed.
Another option: Chipper vacuums, which look like mulching lawn mowers, suck up, pulverize and bag leaves and sticks. They are heavy pieces of equipment, and the best are self-propelled.
What will it cost? Gas chippers and chipper/shredder combos start about $500 and run up to $3,000, depending on power and sophistication. Electric shredders cost about $75 to $500. Chipper vacs cost roughly $500 to $1,500.
Want Alan J. Heavens' advice on a home-improvement project or purchase? E-mail him at email@example.com or write to him at The Inquirer, Box 8263, Philadelphia 19101.