What do you call a short fence made of metal inside a garden used to protect flowers? Is there a specific word for it, or is it just called a short iron fence?
In North America, edging (or sometimes landscape edging) is something that divides different landscaping features from each other - for example, dividing a flower garden from a lawn.
If you want to specify that this edging takes the form of a fence (as opposed to inlaid bricks or stones), it's usually called a garden fence or a garden edging fence.
These fences are sold under two names:
Hoop top fencing panels
Bow top fencing panels
Googling these names will bring up relevant images.