It’s time to put companion planting to the test
Crop rotation and companion planting are just two of the ways we try to get the best from our allotment plot at the same time limiting some of the pests and diseases which can threaten the crops. Both of them are particularly important for organic gardeners for whom running their eyes along the garden centre shelves to select a chemical solution is not an option.
The theory behind crop rotation is pretty simple. Pests and diseases are mainly specific to crop families, so it makes sense to plant each family on a different area of the plot each year to escape the effects of these problems. A four year rotation is good but even that isn’t long enough if your cabbages are affected by club root or your onions with white rot. Then the experts recommend a six year rotation or even longer. The pea and bean family have nitrogenfixing bacteria on their roots and are particularly useful in maintaining soil fertility. The practicalities of carrying out a rigorous crop rotation are more difficult. None of us wants to grow the same area of each crop year on year and so some compromises are necessary.
Companion planting is another technique practised by organic gardeners. Some of the suggestions are based on folklore but very often there is some truth in them. As these practices don’t cause me any problems and often make for an attractive appearance on the plot, I’m happy to go along with them. I always plant some marigolds. Single-flowered strong smelling tagetes can apparently deter aphids and even carrot fly. Calendula, or
Single-flowered strong smelling tagetes can apparently deter aphids
English pot marigolds, certainly attract pollinating insects and look gloriously cheerful.
I’ve signed up to take part in the Great GROW Observatory’s polyculture versus monoculture experiment. The hypothesis is that growing several crops together can help in terms of crop yield, resilience to pests and diseases and enhance wider biodiversity. The effects of growing three or more crops together have not previously been widely studied. The chosen comparison crops are climbing French beans (variety cobra), spinach matador, and cherry belle radishes. Participants in this experiment, starting on 1 May, begin by registering on the GROW website www.growobservatory.org and logging their location. Ideally you need a 1m x 5m strip of ground which in my case is about half the width of my allotment plot. Online support will be available throughout the summer and of course we’ll be recording the weights of our harvests. n