What goes in the trench?
Last season I had a miserable time mowing my yard. I probably have less than 3/4 acre of grass, but it would often take me 2.5 hours or more to mow it due to the numerous obstacles (trees, boulders, retaining walls, and other landscaping features). And during the peak grass-growing season I'd have to mow every 4-5 days. Let's just say that I didn't have much time or energy left for attending to other matters in the yard.
This year I am determined to make my life easier. I bought a riding mower, and more pertinent to the point of this post, I'm trying to make it easier to mow around all those obstacles. To that end, I decided to do 2 main things:
1) Decrease the amount of grass in the yard. This will mainly be accomplished by creating mulched areas and/or planting beds around everything that is a mowing obstacle. I'm also putting in a garden which will reduce the lawn in the back yard significantly. Overall I should be closer to 1/2 acre of lawn when it's all said and done.
2) Add trenched edges between the lawn area and all the new mulched/planting areas. This will accomplish two main things. First it will (hopefully) provide an attractive visual demarcation between lawn area and mulched areas. Second, it will allow me to easily mow up to the edge of the grass. There are hundreds of feet of obstacles in my lawn that the mower couldn't quite get close enough to, and this led to way more line trimming than I ever had time to do. The result was a sloppy look with tall grass and weeds growing around most of those obstacles. Not good!
It's going to take some work to make those trenches, no doubt. I took a leap of faith and bought the Honda FG110 mini-tiller, hoping it would be strong enough to break new ground (sod) and dig me a little trench. I got the tiller today, and after some trial and error, I found that it will work. In about 1/2 hour I managed to create about 50' of 4-6" deep by 9" wide trench around a tree and some boulders. And that's with stopping every 30 seconds or so to dislodge a rock from the tines. Did I mention that the soil here in the Granite State has LOTS of rocks in it?
So now we get to the main point. Once I have the trenches dug, my plan was to lay landscape fabric in the trench and overlapping into the mulched areas. But what to put in the trench? I've done a lot of reading on this and other forums for ideas. Some people just dig a narrow trench with a spade and don't put anything in there. Others dig a deeper trench, fill it with a leveling base like sand, and then top it off with decorative bricks, pavers, or stones. And some fill it with concrete and make decorative patterns on the surface.
My main requirements are that 1) it's sturdy/stable enough that I can drive over it with the wheel of the riding mower, 2) it doesn't need much maintenance (maybe tending to it once a year to fix depressions and the like, and pulling out the occasional weed), 3) it's cheap, and 4) it looks decent.
I think any kind of brick/stone surface is going to be problematic with a riding mower (1). I just can't see them surviving all that weight without becoming dislodged, sunken, or even broken. Not only that, but bricks and pavers would end up being prohibitively expensive to put in the trenches (3). Hundreds of feet of trenches is going to take a very large number of bricks or pavers, and that's going to cost a lot even with the cheapest pavers. I could save money by just using all those rocks that I dig up from the trenches, but I don't think they'd make a smooth/stable riding surface for the mower.
I don't think an empty trench is going to work well, because if the riding mower wheel slips into the trench I'll end up with an uneven cut and/or a scalped lawn and/or a broken riding mower.
My thought was to fill it with some sort of gravel. I don't know much about different types of gravel. but I do know the local nurseries sell pea gravel or "pea stone" for around $50 a cubic yard. For a 9" wide by 5" deep trench, a cubic yard of material will get me about 86 along the trench. That's not bad, as I could probably fill all my trenched areas for a couple hundred dollars.
Would pea gravel, or something like it work for my trenched edge? I think if I tamped it in well it would do a decent job of staying put under the load of the tractor. I think it will look OK. And I think it won't require too much maintenance. Any been-there-done-that experiences I should know about?
Another material that I considered was wood chips. I think that could work fairly well, but I'm guessing they would compact/decompose over time, requiring topping off. And eventually the bottom of the trench would be filled with soil, so I'd probably have more weed problems.
Any other materials or approaches I ought to consider?
PS: I'm shocked that you read all this. :D