A spiral herb garden is an attractive and practical way to grow a variety of herbs in a compact, accessible area. The spiral is built up from the perimeter to the center, with dryer soil at the elevated center progressing to moister conditions at the bottom on the outside. The structure of the garden creates a self-contained permaculture, a form of agriculture that provides the varied conditions for plants with different needs, allowing them to thrive by working together.
The size of a spiral herb garden can vary. Typically a spiral garden might be five to six feet across with a height of two to four feet. This allows the center of the garden to be reached without climbing; larger spiral gardens will have to be accessed by climbing on stepping stones up to the top.
Spiral herb gardens should be built in an area that is flat and receives sun at least six hours per day. The area should be well drained so that no water puddles during a rain storm.
Layout and Construction
Layout of the spiral is straightforward. For example, for a garden 5 feet across place a stick where the middle of the spiral will be. Tie a piece of string measuring 2 1/2 feet long to the stick, hold it taut, and rotate it, placing markers at intervals around the stick. After markers are placed remove all grass and weeds from within the markers and turn over the soil. Then mark the plan for the spiral in the soil. In the northern hemisphere the spiral should move clockwise with the outer end facing north.
A 5 foot spiral will require about 500 to 1,000 pounds of suitable stones or bricks stones depending on how high it is built. Turn over the soil and place stones or bricks in a spiral, setting them about 1 inch deep in the soil. Fill the inside with a layer of gravel. A half inch of gravel is sufficient at the outside of the spiral; gradually increase this layer as you progress to the center, until it is about 1 to 2 inches deep at the center. Fill in to the top of the stones with a mixture of soil and compost, using three parts soil and one part compost. A 5 foot spiral will require 1/2 yard to 1 yard of this mix.
Continue to build the spiral by adding more layers of stone or brick, staggering the joints, with the number of layers increasing toward the center of the spiral. Filling in with soil and compost after each layer before starting the next will prevent the spiral from collapsing as it is built.
Herbs should be planted starting at the top of the spiral working down. Mediterranean herbs that do not require much water should be at the top. Rosemary is a good one for the very center with thyme, sage and lavender next. Plants that require a little more water come next, including herbs such as oregano, tarragon and cilantro. Herbs that need moderate water follow, such as basil, parsley and chives. Near the bottom are herbs that like a moist environment, such as pennyroyal, chamomile and calendula.
How it Works
Water the spiral from the top. The water will trickle down to the bottom providing less water to the plants at the top than at the bottom. The rocks or bricks used to build the spiral retain heat during the day and keep the garden warm during the evening when the temperature drops.
The benefits of a spiral herb garden are many. The plants are elevated as in raised beds and easy to reach. There is little maintenance to a spiral garden except planting, watering and harvesting. A greater variety of herbs can be grown in a smaller space with a spiral herb garden.