How To Build a Herb Spiral
A Herb Spiral is a simple way to improve your kitchen garden, a spiral of rocks encloses soil in which many species of herbs are planted. The rock warms and dehumidifies the soil. The extended edge, wrapped in on itself provides a wide diversity of conditions, creating high productivity in a small space, but is easy to water and harvest.
Scale: A herb spiral is usually about a metre from the middle to the edge, and the center is about a meter above the ground. This is so that you can reach to the center from the outside. It doesn't make sense to make it smaller, because you loose the warming effect of the rocks. You can't really make it bigger, but its possible to put two together in a yin-yang pattern.
You'll need: 1-1.5 m3 of rock, more in a humid climate; 1/4 - 1/2 m3of compost; 20 or 30 herbs; A small amount of cardboard; Friends with strong backs.
Construction: Choose a site close to the kitchen entrance, herbs are best when freshly picked during cooking. The site should get sun, although its fine if part is shaded. This should not be a spot where water pools. Lay out the cardboard in the spiral, this will stop weeds growing up around the rocks, you don't need it in the areas where you will be piling soil.. Arrange the rocks on the cardboard, traditionally the spiral goes in the same direction as water goes down the plug, i.e.clockwise, in the northern hemisphere and anti-clockwise in the southern. The end of the spiral can be blocked with a rock, or you can construct a small pond there, for example a tyre-pond, with a tap over it. As you wind the spiral, you can fill the middle (see the diagram), the small rocks, gravel and coarse sand both ensure drainage and hold heat in the soil. In dryer climates some people just fill with soil and top with compost. When filling with compost pile it high above the rocks, and then wash it down with a hose.
The Herb Spiral offers a variety of niche's for the herbs, at the top in the middle is the dryest soil suitable for Rosemary, getting wetter as the water drains down towards the bottom. Some of the spiral might be shaded by neighbouring bushes, or if something big like bay-leaf is planted, then it will give shade. Take up the niches between the rocks with small herb ground covers like Pennyroyal. Rampant herbs like Basil in the sub-tropics, are better planted outside the spiral. While the herbs are growing to full size, some of the space between them can be taken with small annuals like Rocket.
There shouldn't really be any significant maintenance required, apart of course from picking herbs for the kitchen. Water the herbs at the top of the spiral, how often will depend on your climate.
Herb's and Conditions
Thyme, Sage, Aloe
Basil, Parsley, Cilantro / Coriander
Niches in Rocks:
There is another site with information on building a herb spiral, and lots more about herbs at www.theherbspiral.com., and another article with some pictures on Downsizer.
Credits: Authored by
, from information supplied by Geoff Lawton of Permaculture Research Institute.
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