Keeping bugs at bay with Caithness crop rotation
Gardening on the Edge by Diana Wayland
When growing vegetables, which typically grow for one season before being harvested, it is advisable to plant them in a different location to the previous year.
Called crop rotation, it helps reduce the incidence of pests and diseases specific to one plant type building up in the soil.
This is not necessary with perennial crops like asparagus and rhubarb, or bushes and trees, fruiting or otherwise, herbs, even annual ones, and ornamental perennials.
Rotation will not necessarily eradicate pests and diseases, but it should reduce the incidence of them and prevent them from becoming endemic.
The usual rotation is carried out over a three or four-year period. That simply means that tatties will be back in the bed they were first planted in three or four years before.
Certain groups of vegetables are grouped together for the purposes of rotation. In the four-year rotation they are as follows. Legumes and pod crops; all types of onion; root (carrot, parsnip and so on), solanaceous (tomato etc) and tuberous (tatties); brassicas (such as cabbage, neep).
This is not possible for me because I do not grow sufficient leguminous (beans and pea) to make one rotational year. I also cannot grow tender solanaceous (e.g. tomatoes) outside and some, like sweet potatoes, salsify and scorzonera, I never grow.
So I practice a three-year rotation. Generally, this entails groups as follows: roots, brassicas and others. Others includes solanaceous, legumes (beans and peas), alliums (onions), and leafy plants like lettuce and spinach.
Crop rotation also means that you can follow peas and beans, which fix nitrogen in the soil, with brassicas, which are nitrogen-hungry, or potatoes, which keep down weeds, with onions, which need to be kept weed-free.
Applying manure needs to be done shortly before growing some crops while others prefer it to have been added the season before.
However, I do not use manure or any animal-based fertiliser. Instead I apply seaweed meal and add spent hops and garden compost to increase organic matter in the soil. So I have had to devise my own three-year rotation based on what I mostly grow. That is tatties and some other roots, onions along with leguminous, and brassicas. These, then, are my three-year rotation categories.
Year one therefore is beetroot, carrot, celeriac, parsnip and mostly tattie, the rest one bed each at most. Year two is all alliums: garlic, leek and mostly onions, also beans and peas which take one bed each. Year three is brassicas: broccoli, brussels sprout, cabbage, cauliflower, kale, kohl rabi and neep.
Some of these share beds. Lettuce grows best and gets the least amount of slugs in my woodland garden, so I grow it there every year, just not in the same place.
I rotate the greenhouse crops, too: dwarf French beans, tomatoes and courgettes. I am also trying carrots, as leatherjackets got all mine two years running.
The main proviso of rotation is that, if a vegetable does badly one year, never follow it with one from the same group the following year. So, although my rotation is roots, alliums and brassicas rather than roots, brassicas and alliums, it does not matter because they are all from different groups.
I had to make the alliums one rotation as we do grow a lot. With cloching, they do very well indeed. We have only just finished eating last year’s harvest.
