I'm looking for ideas for sturdy, low maintenance plant bed borders...

Choose something already in existing hardscape and repeat for continuity. In my case it was used brick. When I purchased my house, previous owners had built a slumpstone wall and topped with used brick. So instead of introducing yet another random hardscape material, I purchased used brick from a local building supply that was cheaper than what the big box home impovement stores were charging. I relocated some Texas Privit and replaced with roses.

We used extra brick but they didn't stay in place. Lowe's and Home Depot have bricks with a scooped out ( end and a 'bump end ( that keep them in place. I've got them in my front yard and they haven't budged. Comes in two colors, I think.

How tall do you want your plants? Do you have plants you are alergic to? How much sun will your plants get? Marigolds are especially hardy for full sun, begonias do well in partial shade. It's really about personal taste and location!

Use bricks, landscape blocks, landscape timbers, boards, rocks, fencing, etc. Lots of great options depending on the look and style you are going for.

Thanks everyone!