Do a search on "bed edging" and you'll find some previous discussions.

I use the method you describe. I cut a clean edge in the spring, mulch, and touch up the with string trimmer as you describe. However, I use a flat spade to cut the edge and just lever down on the spade handle to loosen the clump of sod or soil, and then go back and remove the unwanted portions by hand, shaking out excess soil as I go. I don't make the second cut from the other direction because I don't think it's necessary, and I'd have to trample my plants to do it. The sod goes on the compost pile.

I do it as saypoint does, but the sod goes in a sod cake pile, which just means I stack the sod, upside down, in a 3' wide by about 8' long (could be any length) square sided cake. It needs to be at least 2 1/2' tall. Then the pile gets completely covered with a tarp for a year. By the following spring, the sod has decomposed and you have wonderful soil to add to new beds. I usually screen the soil first.

I do the trench edge too but it has become the number one garden chore as the garden has grown in size. Looking ahead to an older future, eliminating the need to edge has become a priority. I have eliminated some edging by placing paths along the beds wherever feasible. But that is not possible or desirable in some areas. So this year I have decided to put in brick edge/mowing strip along the beds I am pretty sure are in their final shape (I have a tendency to revise things often :- ) I am planning to have grass - aluminum edge - 4"x8" paving stone set on compacted screenings - garden bed. Hopefully that will give a clean-looking edge, keep the grass out and make mowing easy. IÂm going to try it out in one small area first to make sure it works and looks good before I do the larger areas. ItÂs the only alternative I can think of to the trench edge.

I installed pavers along the edge (in a sand base). It wasn't hard to do, and they are easily moved if I decide to recontour the lawn. After mowing, I just trim up with a weedeater.

Method of cutting the bed aside, my husband and I have used black edging in several areas. I realize it is not the most natural and some people complain that it is ugly blah blah blah. But it is tough and when installed correctly very long-lived. Personally I love it.

Attaching a picture of a new bed from last fall for your consumption. Still working on filling in that bed but I'm getting there. You really can barely see the edging even but it keeps the lines between bed and grass very well.

Hope this helps.

Kate

Here is a link that might be useful: {{gwi:28139}}

We've got brick for the edgings in the front where there isn't aggregate areas with a bed cut out. In the back, the same thing. At the edge of the lawn is a flat brick mowing strip right up to the raised brick bed. Looks neat and stays tidy easily, it has worked well for us. Just a suggestion. Yes, the hardscape is an investment of $$ but it lasts.

To see pics of what ours looks like with what we have done, ck out my Picture Trail:

Here is a link that might be useful: look at Landscaping Projects, Favourite ROSES We Grow albums

Tip: Instead of using spray paint to mark the outline of your beds just lay out your garden hose and cut along it!

I used a composite edging along my borders. It's a very strong, thin mix of plastic/wood and is a light color that blends in well. With mulch down, you don't even see the edging really. To install, you first have to cut a wedge like some have said but then it gets held down with these special stakes that you can't see from above. It works really well and appears much more durable the black plastic stuff. It is expensive though. Here's a link to what I used:

Link