Recently I’ve been working on a new garden. It’s at the edge of the house paddock, between the olive trees and the boundary fence. We want to turn this area into a “barrier garden” between the main vegetable beds and the rampant kikuyu grass in our neighbour’s pasture. The area faces into the sun, so despite its proximity to the olive trees, I think it will get plenty of light.
Bill Mollison’s Introduction to Permaculture discusses the use of plant barriers to keep invasive plants like kikuyu out of gardens. In particular, he suggests comfrey and lemon grass as good barrier plants against kikuyu. Inspired by these suggestions, I started a whole lot of lemon grass from seed recently, and have planted a line of it along the fence at the back of the barrier garden. The rest of the barrier bed will be taken up with other useful herbs that we’d like to grow, but which are rather too large and/or rampant to put in beds closer to the house. These plants include:
tansy (too invasive to plant in the main garden, but must have it in the garden as it’s very useful for de-worming the goats)
I’ve planted annuals, such as marigolds and calendulas, to fill in spaces in the bed for the time being. Eventually some of these will probably be replaced with valerian and astragalus (milk vetch), which I’m starting from seed at the moment. A neighbour has offered us some more comfrey, so we will probably end up trying that as a barrier plant also.
As with our other garden beds, the area for this barrier garden was covered with black polythene for a couple of months to kill back the kikuyu. Before digging holes for the young transplants, I sprinkled the area liberally with lime and dolomite to loosen and sweeten the clay. Then I mulched with wood chips. I made a barrier of corrugated iron against the fence to keep out the pasture plants until the lemon grass and other barrier plants can establish themselves properly.
It will be interesting to see whether this barrier garden works. If it proves successful, we will probably make similar plantings around most of the edge of the house paddock. We anticipate keeping a further strip of weed mat or mulch between the barrier gardens and the vegetable plots.