How to Build an Herb Spiral

This spring, thanks to COVID-19, most Americans find themselves stuck at home. If you’re fortunate enough to have a backyard, it’s a wonderful escape. But what to do with all your free time? Here’s an idea: Grow food. And while you’re at it, you may as well get creative.

Herb spirals were popularized decades ago by the permaculture movement, a subculture focused on communal living and self-sufficiency. There’s a vague notion about saving space (vertical growing!) and creating different ecological niches (south side for son-loving herbs, north side for those that like it a bit more shady and cool, such as mint). But the main appeal to permaculture hippies seems to be the groovy spiral design. 

Preparation

You can easily have your own groovy spiral planter. Select a flat location that receives at least six hours of sun. In theory, an herb spiral can be as big as you want it, but typically they’re about 6 feet in diameter. Remove the existing vegetation or smother it with a layer of cardboard so that weeds and grass don’t grow up into the spiral later.

Materials

Bricks, cinder blocks and decorative concrete wall blocks have flat surfaces that make them easy to stack into a sturdy bed. Natural stone is also an option, although you may want to avoid it if you don’t have prior experience with stone masonry, as the irregular surfaces make it difficult to work with. You’ll also need bagged or bulk topsoil. Use the formula for the volume of a cone to determine how many cubic feet of soil you need: (π x R2 x H)/3. The height (H) is typically half the radius (R), although you can go up to the full radius if you want a steeper, more dramatic spiral.

Construction

If you want to get professional about it, spread a bed of paver sand or fine gravel as a base to help you stack the building materials perfectly level (not needed if you’re using natural stone). Otherwise, the finished product might look a little crooked and the blocks may settle unevenly, but this is only an aesthetic issue. Mark the shape of the spiral on the ground with spray paint or flour (three coils is good for a six-foot-diameter bed) and lay one row of stone or blocks along this path. Continue laying additional rows, making each one shorter than the last so that the bed slopes gradually upward as the spiral curls inward. Fill the bed with soil as you build it—no need to use mortar or cement, as the earth will hold the blocks/stone in place. Water thoroughly and then top off the soil after it has settled. Then you’re ready to plant.