We live near a sawmill, and when we need boards for our terraced beds we go see what they have in terms of rough-hewn rejects, which are very cheap. Sometimes all they have is poplar, but a few years ago we got some thick hemlock boards that are nice. We use rebar stakes to hold the boards in place, pounded in flush with the tops of the boards. Each spring, we spend maybe an hour replacing boards that have rotted.

Great idea!!! We have a mill not too far away. I'll drop by and inquire. Thanks :)

That is an incredible garden! It's beautiful! I used landscape timbers with rebar pounded in. Worked great. However, plain old 2x8s work well too. Not as permanent, but give some height without being bulky.

Thanks LittleLizzy! We love it and spend most summertime evenings in the garden together, so it's entertainment for us too. I love the idea of 2x8's and the two boxes at the far end of each side are made out of 2 rows of 2x8's, but they are just so expensive and it's a big garden. I was hoping for a more economical solution, but we've just about come to the same conclusion. I think treated 2x8's are the way to go. Thanks!!!

It is a beautiful garden. I agree with you that 4 inches is not high enough. When I built my raised beds, I decided to use landscape blocks since they last longer than wood. Wood is much more simple to erect. Here is what the landscape blocks look like in some of my beds.

Here is another bed near my patio.

If you want your design to look nice, there are not many choices and the all cost a bit of money and work.

Beside lumber, there are concrete blocks/ bricks, genuine bricks, stones.

You may want to rethink the rail road ties, they have a been shown to leach creosolte into your soil.

Try to get black locust. It is highly decay resistant. That's why it is used for fence posts. If black locust is plentiful in your area a local sawmill may be able to supply it rough sawn at a reasonable cost.

Jim