They’re Pretty, But …
Like duct tape, landscape timbers are used for everything but good for nothing.
Landscape timbers are wooden posts, usually eight feet long with a 3-inch by 4-inch profile and rounded edges. They are indeed pretty and versatile. You can stack them horizontally or cut them into short sections and place them vertically in a row.
You’ve likely seen them used for bed borders and raised garden beds. And if you’ve tried them yourself, you know that, within a couple years, they are rotting.
Which is why I hate them. Landscape timbers are attractive and so useful, but they don’t last (NEVER put them in the ground as a post). I don’t know why, but the pressure treating they undergo is simply not enough. For all the work it takes to construct a bed or border, you should get more than two seasons out of them.

How cute! Don’t be fooled.
A Better Option
A standard 4 x 4 ground-contact post will serve you much better, and longer. They don’t have quite the same profile as landscape timbers (and no cute rounded corners). And they are more expensive. But for my money and time, they are the best way to go.
These posts can do everything landscape timbers can but will last for years and years and years.
Another Better Option (For Vertical Applications Only)
One of my favorite landscape materials is the 3 x 3 round fence post. They have a rustic, farm-y feel and are made to last. You cannot stack them horizontally, but they look great for those borders made of short vertical sections butted against each other.
Trust Me On This One
I know you see landscape timbers everywhere, but don’t use them. They are way cheaper than other similar posts, but that ought to tell you something. Save yourself hard labor in the sun and leave them on the shelf.
Kevin