There is probably no other structure as popular for illustrating Permaculture in practice as the Herb Spiral. Okay, I guess I could mention the lasagna sheetmulching method or also the cob oven that tends to be the first hands-on project at a typical Permie intro session. But when it comes to showing how landscape design, zones and sectors, stacking functions, and efficient use of space and water come together in one unique structure, the Spiral Garden is unbeatable.
Turning Theory into Practice
In typical Permaculture Designer Certificate courses, but even in brief intro weekends to Permaculture, there tends to be a lot of theoretical discussions. Since the numerous design principles can be applied to any climatic region, from the tropical to the subarctic, and on any scale from the humongous to the tiny, the practical aspects of the ideas can easily get lost. That's where a good hands-on application comes, where the participants get to move around rocks and dirt, while realizing how much it ties in to the concepts they've just discussed. This way the apparent "main purpose" of "building something to grow all your kitchen herbs on", becomes a neat side feature.
Adjust Your Landscape!
The first thing to realize that landscape is welcome to be modified and adjusted to bring out the best in it. Clearly, while it is important to work with what's there already, it doesn't hurt think about mounds and valleys. And before you bring out the excavators for your large-scale farm, it makes sense to start small... say on a circle of 2-5 meters (6-16 feet) diameter. In other words, the Spiral Garden is a hill with a spiral shaped surface, leading down to ground level, or further down into a water hole. It can be made out of rocks, bricks, concrete debris, or anything else you have lying around that can hold your soil.
Design According to Your Scale
Looking around for existing Herb Spirals it's easy to get confused. Some are so big you can actually climb on them (that is, you have to in order to reach what's growing on top). Others are so tiny that you may not even want to step on them. The question is: which size is the right one for you? Since this is something you will have to decide almost daily in Permaculture, it doesn't hurt starting out with this important question.
Organizing Your Spiral Garden
While there are seemingly endless types of Spiral Gardens, there are a few things they all have in common: They all start out with a region on the top, where water is bound to run off right away, leaving the soil relatively dry. This area is also the most exposed to the wind. Keep this in mind when choosing the plants that are going to live here. Ideally, the spiral should start sloping toward the East from here. Delicate plants that benefit greatly from the morning sun will appreciate this region. As the slope continues toward the South and West, it becomes more suitable for sun loving species. Finally, as the spiral reaches the ground level in the shady Northern part, it will be perfect for herbs that prefer less sun, more shade and more water, since the soil tends to be wetter here. (Note: This is for the Northern Hemisphere. In the Southern Hemisphere North and South are reversed.) To make full use of the runoff water, many people add a small pond at the base of the spiral, where additional aquatic plants, such as watercress, can be grown.
The given illustration offers a good number of herbs for a nicely diverse kitchen. Depending on what else you want in your Herb Spiral, you can add it in the most suitable region. Mint and lemon balm love the cooler, shady part with more water. Lemongrass is great in the sunny area, and tarragon and estragon prefer the dry top of the spiral. Of course, the idea is not limited to kitchen herbs. For maximalists, the same theory can work with a mountain you might want to terraform into a spiral farm. But right now I'd prefer to stay small scale.
Plenty of Benefits (That's Why It's Permaculture)
As explained above, the main purpose of the Spiral Garden is not only to increase your gardening area by making use of the vertical, but also to create diverse climatic conditions, which do make a difference on the smallest scale. But as Permaculture tends to be, there are many other benefits to it. The structure itself offers great habitat for numerous animals, such as frogs, salamanders, lizards, but also pollinating insects, and of course others that may not directly benefit us, but by feeding on others they all add to the stability of our ecosystem. The structure itself will suppress weeds and make use of material that you're not likely to use elsewhere. Finally, depending on the size and location, it will be an ideal place to grow all your kitchen herbs right where you can access them most easily.
Some Things to Keep in Mind
- When building the structure, make sure it will contain the soil in a nice trough, slanting slightly inward. That way bits and pieces that fall off will roll towards the center, until contained by the main mound.
- Make sure the slope is always nice and gradual, avoiding sudden drops where the water can rush down quickly, eroding the soil.
- If you're going to walk on your spiral, include a separate walkway that won't compress good soil. Most importantly, it should be sturdy enough to provide stability and make access safe.
- Don't forget that while the structure is important to keep the soil in place, it is the soil that you'll be growing plants in. So it should have a good depth of 20-50 cm (8-20 inches) throughout the entire spiral. This can be the trickiest part!
- Apply your own observation to which plants do better in which parts of the spiral. Also, with time you will find many other plants growing in it that you didn't plant. Before removing them, consider how much they actually bother your herbs, and whether their benefits may not outweigh their drawbacks.
Go Out and Build Your Own!
I hope this brief overview got you inspired to go out and try building an Herb Spiral yourself! I would love to hear your experiences with it!