An herb spiral is a compact, low-maintenance raised bed garden that works with what are called microclimates, small areas of cultivation that provide uniquely suitable conditions for carefully selected plants.
“Herbs” in the sense I’m referring to them comprise a culinary—not botanical—category. These are fragrant plants that have historically been used to season food, often containing essential oils with strong flavors and antimicrobial properties.
Plants that require the most drainage and heat are placed near the top, and on the sides of the spiral, with the warmest exposure (usually south in the northern hemisphere). Ideally, the spiral garden is built with stone or brick, which have a high heat capacity: These materials absorb solar energy during the day and release it in the form of heat at night. This is helpful for plants like rosemary, lavender and tarragon fare well in a hot and dry microclimate.
Plants requiring more moisture, shade, or shelter (thing dill chives and chervil) are placed lower on the structure. The water that drains from the soil higher on the structure accumulates in these lower areas, and the differences in grade allow for shelter from wind and excessive sunlight.
Weeding requirements are minimal, as the planting is so dense. There’s not enough space for many uninvited guests—aka weeds—to colonize the soil.
Cultivate an herb spiral with plants that “play well with others.” I avoid putting mint in the spiral garden because it’s quick to choke out the less-invasive selections. Otherwise, a wide array of culinary herbs can be grown in a space under 5 square feet and harvested at a more comfortable height.
This garden is easily built with free or salvaged materials, and can be personalized in a variety of ways. I added a little wattle fence to the side of mine, and plugged the holes between the bricks with succulent Sempervivum plants.
Every herb spiral has a personal touch: Using local or salvaged materials to build the garden, and selecting the plants used in favorite dishes makes each garden totally unique.