Building a Herb Spiral

Watching a spiral herb garden being constructed is a fascinating thing. Having 50 school kids building it all at once can descend into mayhem, but fortunately Permaculture teacher Leonie Shanahan was able to keep the whole process on track with a certain degree of military precision. After many weeks of planning their own school garden project the kids were now allowed to dig up the school grounds and build their little garden beds. Their designs were assessed and it was agreed that “love hearts” and spiral gardens would be constructed. Ecofilms were there on standby to film the event and despite the light shower or two of rain, the kids worked like beavers under Leonie’s expert direction – although she was losing her voice by the end of the day, she did mention that it was due to a virus – and not the kids that she was yelling at. Anyway on to the herb spiral.

The Herb Spiral

A herb spiral is like a little mountain in your backyard that has a spiraling stone border that if placed near your kitchen or backyard takes up very little space but can also grow a multitude of kitchen herbs and create its own mini-micro climate. The top of the little mountain heap will be sunny and dry out a lot fastest so its ideal for plants that require less water and enjoy plenty of sun. The plants at the base will be more moisture loving and you can add shade loving plants into the mix and even a little frog pond and lizard habitat that will keep the bugs in check. By building a multi-deck system like this, you are in fact creating a multi-story little ecosystem right at your front door that can also favour a variety of herbs suitable for the kitchen.

Dimensions

The herb spiral garden should not be too big if you want to get access to it. It can be around a meter and a half in width so your hand can easily reach into the centre from any side. The height is about a meter tall.

Leonie Shanahan’s spiral herb garden was created by marking out the boundary of the garden bed using a string tied to a stake to mark out the boundary of the garden bed. The boundary perimeter was dug out with a shovel and the waste was piled into the centre to create the bulk of the bed that will make the mound.

Newspaper was placed into the trench to prevent weeds from sprouting. The heavy stones were then laid into the trench to define the base of the garden bed. When laying out newspaper to prevent weeds from sprouting make sure you apply it in thick layers.

Permaculture teacher Geoff Lawton favours the thick Sunday editions, laid out complete – not opened.

Geoff says telephone books would make an excellent alternative. Many beginners make the mistake of putting too little newspaper down at the start. Remember it will all break down eventually and make good soil. Start with a solid foundation. Use plenty of thick newspaper.

Zones

When the stone boundary is completed, its time to build up the soil mound to at least a meter in height. This is important as the height will allow at least three zones of herbs to be grown.From the dry Mediterranean herbs at the top of the mound like Rosemary, Thyme and Oregano, the kind of herbs that prefer a dry soil.

The middle zone will allow tomatoes and basil to thrive and the bottom zone will allow more sensitive and moisture loving plants like mints and water cress to grow.

Building Layers into the Mound



Leonie likes to layer the spiral garden mound with a mixture of compost layers that help build fertility into the garden bed. So a layer of spent mushroom compost alternating with worm castings is a good start if you can get access to this material.

Over this layer she’ll instruct the kids to do a scatter mulch of lucerne hay to add organic matter into the soil. Other trace elements she uses in the mix are seaweed minerals like Natramin which will give the plants all the nutrients they require to grow well. A thin sprinkle of Dolomite is also added to balance the pH of the soil.

And then the layers are repeated like a lasagna of compost, mulch and additives until the peak of the garden bed is formed.

Resting the Garden

Once the spiral stone work is in place, the straw mulch is applied and the whole spiral herb garden is rested for about two weeks.

Frog Pond

Adding an optional little frog pond at the base of the herb spiral adds a little predator habitat. Once the system matures, you will notice, frogs, lizards and birds congregating around your herb spiral and knocking off any caterpillar or bug that comes into your herb garden.

We’ll follow the progress of this spiral in later posts.