When you work for Consumer Reports, friends, family, and acquaintances often are curious about how we examine products, wondering if we really do put each and every item—be it a vacuum or a Volkswagen—through rigorous testing.

For string trimmers, an essential yard-care tool, I can tell you, based on first-hand experience, that a lot of work goes into reviewing these machines.

One day early last fall, despite a looming deadline, I snuck off for a ride to Lyndhurst, a New York country estate once home to former New York City mayor William Paulding and railroad tycoon Jay Gould. This 67-acre property north of our Yonkers, New York, headquarters includes a nearly 170-year-old Gothic Revival mansion. The National Trust for Historic Preservation, which maintains the site, has let Consumer Reports test leaf blowers and string trimmers there for more than 10 years.

Running the tests that afternoon were Peter Sawchuk, our outdoor-power-equipment maven (shown with the highly rated Stihl FS 45 gas-powered string trimmer), and Mike Sedlak. I caught up with them as they were whacking away at tall weeds and grass on a little-used portion of the estate along the Hudson River, testing the 21 new gas and electric models that will appear in our upcoming review of string trimmers. (You’ll find the new story on our string trimmers page along with updated Ratings and CR Quick Recommendations, available to subscribers.)

I watched Peter and Mike run the grass-and-weeds test, which replicates the worst conditions you might encounter along the perimeter of your property—some of the growth is more than a yard high and is rife with deer ticks and poison oak. They timed how long it took each model to chop the grass in a 5x8-foot patch down to about three inches. They also tested the edging capability of each model along wood pilings and some of the walkways.

Our testers also assess each string trimmer on how well it’s balanced, how easy it is to replace cutting line, and how noisy the machine is at the operator’s ear.

The testing at Lyndhurst might not have been as much fun as my machete-swinging hikes in the boonies of Guam . . . that’s another story. But from all appearances, the best weed whackers we tested are far more precise.—Ed Perratore

Essential information: Read about the pros and cons of gasoline and electric trimmers and learn how to find the right model.