If you’re lacking space to grow herbs, here’s a solution popularized by Bill Mollison, pillar of permaculture: the herb spiral.
I’ve done all the research into why, where, and how to build an herb spiral so you won’t have to. You’re welcome.
Why Should Someone Build an Herb Spiral?
My kitchen window sill is already overflowing with basil, chives, and thyme. But I don’t have enough space to grow all the varieties my cooking requires. What about rosemary? Mint? Sage and garlic? Unfortunately, I don’t have a south-facing 15-foot window sill at home. (Does anyone?) But I do have a bit of lawn to work with.
As such, the herb spiral is a great design for small spaces. This garden type is shaped like a spiral, 2m (6ft) wide, with its center raised by about 1m (3ft), sloping down to ground level.
What Makes This Design Work?
Everything that grows in there is easily accessible. With the garden’s center only 3ft from the edge, all you need to do is reach for the herbs you need. There’s no careful treading or stepping stones required.
Its compact size also makes weeding and watering a breeze.
But here’s the real magic: the garden’s shape creates many different microclimates. The top of the spiral has better drainage and more sun, perfect for plants that love light and prefer dry feet. The lower the plant in the spiral, the more water it gets.
The amount of sunlight and heat also varies depending on the position in the spiral. The eastern side stays cooler than the south and west facing sides, because it gets no afternoon heat. And the north side is mostly shady.
Building materials also play a role in providing an optimal environment for your herbs. The stone or brick walls will absorb heat during the day and warm the garden at night.
Keep Your Ingredients Close
The spiral garden’s contents are mostly destined to be chopped, cooked, or steeped. Therefore, it’s best if you set it up as close to the kitchen as possible.
Remember Bill Mollison? In one of his permaculture trainings in the 1990s (which was recorded and is available here), he shared his rule of thumb to find the best place for an herb spiral. He said that you should be able to get fresh greens from your herb spiral early in the morning without getting your slippers wet.
If your slippers get wet, you’ve built it too far away.
The idea is to have your herbs within reach—both to take better care of them and to harvest them often. “In your sight, in your mind,” one could say.
Your spiral should be easily accessible and easy to walk around. It’s important for you to be able to reach every nook and cranny of the garden for easy watering, weeding, and harvesting.
If you’re building an herb spiral in the Northern hemisphere, orient the base of the spiral towards the north. In the Southern hemisphere, make it point south. That’s to reduce evaporation and maximize water retention. Also, that orientation will provide more shade for the plants that wouldn’t thrive well with a full day of direct sunlight.
Make sure the location has lots of sun and is well drained. A bit of lawn space will work marvellously. If all you have to work with is a cement slab or a balcony, you could build the herb spiral as a raised bed, or use a large grow bag.
How to Build Yours
Let me say this right here: there are as many methods to build an herb spiral as there are herb spiral builders. This isn’t a one-size-fits-all, cookie-cutter method, but rather a general guideline for you to use. It’s highly adaptable and customizable, so you can adapt it to your own needs and aesthetic preferences.
That said, I’ll present here a method inspired by Bill Mollison’s own work on the subject.
What you’ll need:
- 6-7m2 (65-75 sq ft) of cardboard, newspaper, or gravel
- 510-565L (18-20 cu ft) of rock, brick, or stones (edging materials)
- 565-705L (20-25 cu ft) of soil
- 200-280L (7-10 cu ft) of mulch
- Enough seeds or seedlings for a 14-15 sq ft garden
Setting The Foundation
Once you’ve garnered all the materials you’ll need and chosen the perfect spot for your herb spiral, it’s time to get to work.
First, mark a 2m (6ft) circle. You can use a stake planted in the ground and a 1m (3ft) length of rope to do so. If you like, you can also use pegs or small rocks to delineate the area that the garden will cover.
If you’re building the spiral on an existing lawn or on a dirt patch, use cardboard, newspaper, or gravel to cover all the ground within the circle you’ve marked. This first layer of material will serve as a barrier between grass and weeds in the existing soil and your garden.
Make sure to wet the cardboard or newspaper thoroughly. Doing this will speed up the decomposition of the fibrous material, turning it into food for your herbs much more quickly.
Also, it stops it from blowing away in the wind.
If you’re not using any mortar to hold your bricks or stones together, pile about 2ft of soil in the middle of the circle. The pile should spread almost to the edge of the circle. By doing this, you make it easier to place the edging material, using all that dirt to support it.
If you’re using mortar, save the dirt for later.
Make sure to mark the lowest part of your spiral (north in the Northern hemisphere, south in the South). That’s where you’ll start building the walls.
Building the Spiral
Now that your base is set up, it’s time to draw a spiral and lay the stones or bricks. You can use string or pebbles to mark the spiral as a guideline for the larger building materials. As a basic rule, your spiral should wrap around itself twice.
Starting at the lowest, widest point of the spiral, lay the first 15cm (6in) layer of the wall, all the way to the middle. Pack some soil around these to make sure they’re as stable as possible.
Then, about 60cm (2ft) from the beginning of the wall, start the wall’s second layer. Again, add bricks or stones all the way to the middle, and add more soil for stability. Lean them slightly inwards to have very solid walls.
Once the second layer is done, add the third layer, starting 60cm (2ft) from where you started the previous one. By adding a new 15cm (6in) layer every 60cm (2ft), the center planting area will end up at 1m (3ft) high.
Now that the walls of the herb spiral are up, you can fill it with the rest of the soil. Don’t forget to water it until it’s damp (but not soggy). This first watering will compact your soil a bit, so don’t hesitate to add more. As a bonus, your seeds and seedlings will have water right from the get go.
Finally, add a thick layer of mulch to trap all that good moisture.
Planting Your Herbs
After all that hard work, you now have a gorgeous garden bed just waiting to welcome all those savory herbs that your kitchen needs.
But which plants should go where? Knowing the microclimates around the spiral and the your plants’ individual needswill guide your planting decisions. Here’s a quick rundown for common herbs.
The top of the herb spiral is sunny and dry, and has the most space to offer for deep-rooting plants. It’s a great spot for a bay tree. Other great candidates include perennials like rosemary, lavender, sage, oregano, tarragon, marjoram, thyme, and garlic chives.
In the shade of these plants, still high and dry in the spiral, you should plant shade-tolerant plants. Why not attract pollinators with yarrow, nasturtiums, and parsley?
In the middle of herb spiral, the soil will be damper. The sunny side offers great conditions for coriander, sorrel, basil, chives, and strawberries. On the shady side, go for chamomile, arugula, and borage.
At the bottom of the garden, the soil is wet. The spiral’s slope allows gravity to pull water from the top to the bottom. The sunny side will be perfect for chamomile and mints. Just keep in mind that mints tend to be aggressively invasive. You could plant it in a clay pot to control its spreading. Otherwise, it’ll invade its neighbors.
Finally, at the very bottom of the herb spiral where it’s shady and wet, lemon balm and cress will thrive. You could even build a little pond there to add a few aquatic plants like water chestnuts, watercress, and arrowhead.
If that’s still not enough herbs for you, try this: fill the gaps between plants by planting rocket, spinach, or lettuce. You’ll be eating savory salads all year!