Transforming Gardens with Corten Steel: A Modern Touch with Rustic Charm

By Grace Hensley, Fashion Plants

When I built my garden this spring, I was inspired by June Blake's Irish Garden with her low reflecting pool, and specified one long Corten steel trough to echo the shape of the cutout on my patio. In a fit of madness I ordered two, and now have a circular pool waiting for its garden to be designed around it.

Corten adds a modern, yet rustic element to all types of gardens, from charming cottage farmhouses like mine to stylish modern abodes. It is an alloy of steel that includes copper, chromium, and nickel that oxidizes, and the distinctive orange rust forms a protective layer that prevents further corrosion. It was invented in the 1930s as a corrosion resistant (COR) material with a high tensile strength (TEN), to move heavy iron ore. COR-TEN®, has been used in art and architecture since the 1960s including the striking Picasso sculpture in Chicago's Daley Plaza. Corten is now the commonly used generic name for this kind of weathering steel.

I was so delighted when I filled up my shiny new pool, and splashed happily, until the steel began to rust turning the water cloudy. I knew the exterior was supposed to oxidize and form a protective rusty layer, but I didn't realize that the inside wouldn't stop rusting when constantly wet! Ideally, to speed up the formation of this layer, you should alternate periods of wet and dry, above 50 degrees; easy in the Pacific Northwest, right? However, the first layers of this oxidation process are fairly fragile and can brush off, staining other materials like the concrete pavers it was resting on. As a side note, Corten isn't as long-lasting around chlorine swimming pools or in subtropical, seaside environments, where the patina doesn't stabilize. In my case the patina kept flaking off into the water.

APLDWA member Jade Waples, Designer and co-Owner of Orion Rockscapes, uses Corten beautifully as edging, raised garden beds, and retaining walls. She sources her pre-measured (and measured, and measured) panels from Everett Steel, and her crew welds each labelled panel together on site. With suction cups and panel dollies, the heavy pieces can be maneuvered into back yards and awkward spaces. "Having the right tools is essential," she advises. This newly installed garden was designed by Wes Pierce, creating terracing and different garden beds. Garden designer Danielle Mecham now has space to play with varying plant choices for this beautifully modern garden.

Jade adds that Corten is a versatile material; she used it in combination with Ipe wood edging attached to angle steel on these raised beds in her parents' garden. I love how it solves the problem of having a comfortable place to sit while tending your plants.

This modern front yard is transformed by the Corten retaining walls, designed by Pierce Design and planted by Danielle Mecham. Orion Rockscapes completed the installation. Photo courtesy of Jade Waples, Orion Rockscapes

These charming raised beds with Ipe trim fit both modern and country garden aesthetics. Photo courtesy of Jade Waples, Orion Rockscapes

These street-side raised beds were easy to install with simple tools, and turn unused space into a productive vegetable garden. Photo courtesy of Sally-Anne Sadler, Shooting Star Gardens

Sally-Anne Sadler, owner of Shooting Star Gardens in North Seattle, prefers rolled steel ordered in custom sizes from Everett Steel for her edging, raised beds, and retaining walls. Less expensive, and almost as long-lasting as Corten, rolled steel is easy to work with. You can weld custom pieces or drill holes in the sheets to fasten lengths together (using galvanized fittings and nylon spacers). Other metal alternatives to Corten include galvanized steel, with its shiny zinc coating, or a chromium-based stainless steel. I even took my vintage metal garden tea-table to be powder-coated in my signature blue; for small portable projects this would add a splash of color.

Over several weeks, I carefully drained and dried my new pool (it was March, so this took me quite a while). Although I had a hose-spigot attached, I ended up using a bilge-pump to get it entirely dry so I probably wouldn't bother adding a drain hole next time. I then accelerated the rusting with an over-the-counter formulation of muriatic acid I poured into a spray bottle, wetting it down after 24 hours, and then repeating that until I had a base layer of rust that I liked. You can also use a solution containing 1/2 tsp salt, 2 Tbsp of vinegar, and 2 cups of hydrogen peroxide solution and apply it with a simple pump-sprayer but the examples on YouTube showed a more uneven patina for my preference. After this, I applied a thick layer of polyurethane with a sponge brush to seal in the rusted layer, because I didn't want it to continue to rust and flake off into the pool. If I had skipped the rusting step before painting, the steel would not retain the corrosion-resistant properties that I wanted. However, I am letting the exterior of the pool rust in its own time; I am eager to see how it turns out.

Newly installed reflecting pool will slowly gain patina over time. Photo by Grace Hensley.

Corten can be used in a variety of creative ways in the garden. Long, narrow, 8" or 10" strips of sturdy 11 gauge, or more pliable 14 gauge strips, can be used as path or garden bed edging. Skill with welding will make a nice seam, or you can butt or overlap the layers as you go, and pin them into place with Corten stakes. Wider strips of 12", 18", or 24" can be welded together for a variety of raised bed options. Sweeping curves can enhance your planting scheme, or be used as dramatic sculptures.

This curved Corten wall at RHS Harlow Carr encloses a bench. Photo by Grace Hensley

The iron-oxide patina that forms from rolled or Corten steel is non-toxic to plants, and safe for growing food. If you're placing them directly against concrete, be prepared for some staining as they start to weather, or plan to cover the ground with gravel or wood chips. Jade Waples recommends leaving a slight sand-filled gap between concrete and Corten edging. A vinegar or muriatic acid wash and some elbow-grease will remove the rust stains on the concrete, but who needs the extra work?

Andrea Whitely, a garden writer and designer in Perth, Australia, uses Corten steel in most of the gardens she designs, for retaining walls, lawn edging, water bowls, and circles around fire pits. Her only complaint is the wayward cars which tend to bend them out of shape, so she "bangs them back into shape with a rubber mallet and my brutish strength", she quips. Your imagination is the only limit for using Corten steel in gardens.