Is this like galvanized steel? It may eventually rust out on you.

Thanks for your response, Seil. It is similar to that, yes. From what I've read, the difference is that galvalume is a zinc and aluminum alloy that coats the steel, making it longer lasting. But you are right-- it would probably rust eventually. I don't know how it would interact with the road salt that they use here in the winters. I also don't know the difference in longevity between a metal border and one made of untreated wood. I'm pretty new to all of this.

Eventually I think just about anything will fail. I have some paver edgings that are starting to fall over, some treated wood that is starting to rot and some of that plastic edging that buckles and heaves nearly yearly. It all goes eventually. I would give it a try. It can't be any worse than the others.

I don't know how long of a section it is, but you could possibly find some salvaged red brick to lay on edge, or buy a pallet for relatively cheap. They run about 40 cents a brick here. So less than a dollar per foot. Nice in ease of placement and eventual re-leveling, and has a fairly traditional and sturdy appearance and can be repurposed if you want to make it taller use for another application later. It also has the advantage of not having a sharp edge in the event of falling and not being subject to warping. Just an idea to ponder.

I suggest you use pressure treated 1 x 4 or 1 x 6 inch boards. Cut the boards in 8 inch lengths then cut the corners off at one end of each board. Next dig a trench around the bed, inserts the boards vertically so that notched end and 5 inches or so are above ground. Back fill around the boards and you have a boarder that can easily be replaced, expanded, and/or relocated as needed.

We make our chicken runs from 2x4 treated boards and they even rot here in the humidity in about 2 years. Bricks and cement blocks seem to last. Rebar seems to last. I have had several metal trellises rust rot and break. I just pulled the last one down last week. It was a large arch and was so cute and had a gate too but alas they all rust.