It can be done; like all cement projects, the main effort is in the prep work. You can use plain concrete and blend in sand you get separately, or you can buy a concrete mix. You can also get into hypertufa formulations, but while hypertufa makes great planters and ornaments, and is okay for low edging, it really is not strong enough for walking on much less rolling a riding mower over.

There are several differemt ways of doing the edging, depending on just what final result you want. The ones that (I think) are best are done by digging the trench as wide as you want (mine are wide enough -5"- to roll the mower wheel along) and about 6" to 8" deep. Make the sides straight up and down - don't slope them in. I line the sides and bottom with heavy-duty landscape fabric to prevent grasses from growing under the concrete and into the flower beds, but that is not a have-to-do. Sand is put down and packed to 3"- 4". (Or a couple inches of coarse gravel, topped with a couple inches of sand.) Then the concrete is poured to about gound level. Takes a lot of concrete! But this is the sort of project that can be done a bit at a time if you like. You can use less sand base and even less concrete, but you greatly increase the chance of frost heave and/or breaking up if you use less than 2"inches of sand and 2" concrete. You can embed brick pieces or larger stones to make a pattern, just be sure to keep the surface fairly level. I didn't on one bed and for three years now I've been going whoomp! as I'm mowing along and then hit the raised stone - but breaking up the concrete and re-setting the stone is not something I'm eager to do.