What is your proposed budget at this point?

How far is your garden from the place that you intend to store the tiller?

Essentially, tillers can be divided into four camps.

Rear tine - This are the real workhorses. They have inflated tractor style tires, multiple forward speeds, reverse gear and the rotating tiller section is located at the rear. This is what I use. Experience has taught me that this is the best design.

Mid-tine - Honda makes a mid-tine tiller that is a rental yard favorite. The engine sits slightly forward of the rotating tiller section. If I couldn't afford the rear-tine, then this would be my second choice. I have used this tiller and prefer it to the front tine. But after owning and operating a rear-tine.......the mid-tine would make me crave the rear-tine.

Front-tine - These are the lowest cost tillers. Many people, myself included do not like this design. The engine sits directly over the rotating tiller section. I find that they bounce around too much and you need to put a lot of effort into controlling them when breaking ground.

Mini-tillers - These are small, light units that don't dig very deep. Excellent for weed control and their size allows you to get into tight areas after everything has been planted and is now growing. Honda and Mantis both make excellent units.

I strongly advise against using your tiller in rocky, root infested ground. It's not only hard on the tiller but when the tines hit immovable objects, Newton's law comes into play. The tiller is thrust into the air and the handles can slam into your body if you are leaning over the tiller. You use the term boulders and to me, that means rocks larger than eight inches in size.

If you have rocks that large, then you should use a mini-excavator to dig this area initially so that all the large stuff can be cleaned out. The mini-ex will easily rip through roots that are three inches in diameter and remove boulders up to two feet in size. You can hire someone with a mini-ex to do this work. Once all the large junk is removed, you can add soil amendments such as peat moss, sand, loam and compost in successive layers and rototill each layer in prior to adding another layer.

Once your soil has been properly built, your tiller will have an easy job of churning through it each spring and fall.

Troy-built, Merrytiller, Ariens, Honda, BCS, Gravely are all good quality tillers. I suggest that you try going to the rental places and see what they offer. Rental stores choose easy to use, long-lasting equipment that they can sell easily when they are done with it. If you can figure out the tiller type that best works for you, then you can often find a really good used unit for very low cost.

Use ebay or your local classifieds or Kijiji or Craigslist. Good tillers last a long time because they only see a few hours of use each year. Condition and brand are what's important. A well-cared for 15 year old Troy-built tiller or Merrytiller often turn out to be excellent buys.

"There are areas of my garden that are full of tree roots, rocks and boulders and compacted soil. I also would like to be able to use it to mix compost, etc. into existing beds."

Any tiller, including the little Mantis models, can mix compost and such into existing beds. Like you, I have the "tree roots, rocks and boulders" in abundance, so I use the top-of-the-line mid-tined model, the Merry Tiller, International model with the Honda engine option (although the Briggs & Stratton option is also very good.) On that link, scroll down to see some of the available accessories.

The key advantages of this tiller are the controllable high torque and slow tine speed provided by the triple reduction sealed transmission and the heavy duty twin V-belt clutch. When you encounter a rock, you can often let the clutch slip a little, while still delivering torque, as you roll the rock out onto the surface.

I've rolled out some surprisingly large rocks. I keep a metal "rock bucket" handy to toss the smaller rocks into, but the larger rocks get carried individually to the rock pile. My slow tines speeds of 30 RPM to 65 RPM, depending on the throttle setting, make my encounters with rocks and roots and such much less traumatic than the high tine speeds of rear tined tillers. Encountering a big rock with tines whirring at speeds up to 300 RPM would be a little bit more excitement than I would want.

Since the tines are turning slowly, it doesn't throw dirt, so no dirt shield is needed, and you have a full, unobstructed view of the tilling zone. That's handy in case something interesting comes to the surface. I even dug up a Timex watch once (it wasn't still ticking). I have discussed the advantages of the Merry Tiller International mid-tined models at more length in other forum messages, if you want to do a Search.

The Merry Tiller is a versatile machine because so many accessories are available. I even bolted a piece of 2x6 board to my plow bar to improvise a dozer blade to help make our garden more level.

MM

"...is that a retaining wall built out of ~18" lengths of tree trunk?"

Yes, it is. It's actually a terraced strawberry bed in three "stair step" levels. My main garden (the one that is being leveled in the picture) is also a large terrace, retained by a different style of tree trunk retaining wall, that currently ranges from 3 feet to 5 feet high.

This property is very sloping and wooded, and I have found that the "tree blocks" are a convenient available "free" material for landscaping construction. I use lengths ranging from 8 inches to 20 inches, depending on the height of the needed terraces. I also make stepping stones from 4-inch to 6-inch slices of tree trunk. The tree blocks are versatile. I have a good chainsaw, and I get a lot of use out of it. You're right. There is a lot of work to be done on this property.

MM

Your soil looks in good shape and nice to work in as your tiller is in nicely. Looks like you get good crops even with your shorter season.

If you are trying to grow a garden, the tree roots are going to sap the soil and starve whatever you are trying to grow. In the past my approach to roots has been to cut them out.

The trees and shrubs have other roots that they can use and expand upon, so hopefully they can adapt to your tilling. I would fire up that tiller and tell those trees and shrubs to send their roots elsewhere.

MM