use 5mm non galvanised mild steel edging to contain lawn gravel areas and gardens from one another. Within a couple of weeks the metal has reacted to the moisture in the atmosphere and turned a rust colour. this style of edging is complimentary to both old and new houses
Landscape Edging: 10 Easy Ways to Set Your Garden Beds Apart: EverEdge Edging - Made from sturdy, powder coated flexible steel with 3-3/4" spikes, EvrEdge appeals with its casual, country garden look. Lengths are interlocking for seamless installation and come five to a set, totaling 16 linear feet of edging per package. $95 at Grandin Road
The simplest and most subtle borders that effectively separate your lawn from a garden are 4-in.deep strips of steel, aluminum or plastic. They all bend easily into smooth, graceful curves and stop the spread of grass roots. However, painted aluminum and steel offer the sleekest, most refined look because they almost disappear against the grass and garden bed.