A mechanical tiller makes mincemeat out of the hardest job in the garden: turning the soil. The only hard part is choosing (from among the hundreds of models, sizes and special features) which tiller is best for you and your garden. To help you decide, ask yourself, "How much power do I need? How big is my job? How hard do I want to work?" To decide between renting and buying, ask, "How often will I use it?"
Some things to consider:
Most tillers have an accelerator on or near the handle or on the engine. On front- and mid-tine tillers, the speed of the rotating tines helps determine the speed of the machine, and you supply the drag.
The smallest rototillers operate on less than one horse, whereas the bigger ones need 8 hp to pull them through the soil.
On rear-tine tillers, wheels are standard operating equipment. On smaller tillers wheels are used to roll the tiller to the garden, then are removed and replaced with a drag bar (which helps control forward movement and depth of tilling) before you start the job.
Bolo tines are best for cultivating established beds and working organic matter into the soil. Longer digging tines are designed for cutting through tough sod and working deeply. Mini-tillers have closely spaced tines. If you have rocky soil, you'll want a tiller that allows you to turn the tines outward. This will prevent rocks from getting stuck in them. Otherwise you'll be stopping often to knock out rocks.
Some tillers cut a path seven inches wide (and even skinnier if you remove a tine or two); others, three feet. Some cultivate five inches deep; others can easily burrow a foot or more. The tiller pictured cuts a nine-inch-wide swath.
Front- and Mid-Tine Tillers
The tines on front-tine and mid-tine tillers are in front of or just beneath the engine. The tiller moves forward by the action of forward-rotating tines as they dig into the soil. Front-tine tillers are good multipurpose machines, and because the tines are in front, you can till close to obstacles. They take a lot of muscle to manage, and depending on your soil, you usually have to make multiple passes to work the soil fine enough for planting seeds.
The tines on rear-tine tillers — located behind the engine and the wheels — typically rotate backward. These heavy, more expensive tillers can convert sod into fine seedbeds with a lot less effort on your part than other tillers. They have powered wheels so you can one-hand it and not walk in the tracks, but because of the drive shaft, you can't till very deep. Rear-tine tillers are excellent for large jobs: tough soil and large gardens.
Weighing 19 to 25 pounds, minis are great for small- to mid-size gardens and ideal for cultivating close to plants in already established beds. They're also good for digging holes for planting trees and shrubs. Forward-rotating tines pull a mini-tiller forward, and there's sometimes some bounce to these machines, so the heavier models within this size class are usually best at staying grounded. Controlling the depth at which you're tilling can be tricky, so if evenness is your thing, you'll probably need to use a rake to smooth the bed.