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Mixing it!

Crop rotation has long been at the heart of veg plot planning. But why do it and how should we go about it? KG's Steve Ott explains

To the disorganised gardener the thought of crop rotation can seem like a real chore. “Why bother? I never have and my crops are always OK,” is one common comment. It is true that if you never rotate your crops, that is grow related vegetables in family groups, they will grow. You may get away with it for some time, too... before things start to go wrong. Yes there are sound reasons for doing it and sooner or later if you ignore the advice, your crops will suffer. So what benefits does crop rotation bring?
There are three main reasons to move crops around the plot each year and they are:

• Related crops tend to attract certain pests and diseases (eg onions/white rot, cabbages/club root, potatoes/eelworm) which build up in the soil. Rotation avoids this.

• All crops need differing levels of nutrients. Grown on the same soil year after year, they will take the plant foods they need most from the soil, depleting them until growth is affected. Some crops such as peas, actually add nutrients to the soil, benefiting those following on.

• Some crops are better than others at smothering weeds, potatoes and squashes, for example. Grow them on a patch of soil every three or four years and they can greatly reduce the number of weeds.

How long should my crop rotation be?

The answer is, as long as possible. However, it is seldom practical to use more than a three or four year rotation. On very small sites you may only be able to have a 'notional' rotation. In other words, just keeping in mind that while you don't have room to divide your plot or border into three, four or more sections, you will be careful not to plant related crops into the same patch of soil.

How do I start?

Start now, before sowing any crops this year. Simply divide your plot into the required number of sections – three for a three year rotation, four for a four year plan. If you have raised beds planning is easier since visualising that plan is simple, but this is certainly not essential.

Which crops can be grown together?

Related plants are safe to grow together. On top of that certain unrelated plants requiring similar conditions, will often make good bedfellows (see diagram).

The longer a rotation you can operate, the more refined can be your groupings. A three year rotation allows for relatively simple groupings such as brassicas (cabbage family), roots (carrots, potatoes and beetroot) and everything else (tomatoes, sweetcorn, spinach, onions etc).
With a four year rotation you stand a better chance of keeping pests and diseases at bay by having more refined groupings (see diagram). These include:

Plot 1: Potatoes, tomatoes, peppers and where they can be grown successfully outside, aubergines. You can also add the cucumber family here to help smother weeds. In winter – overwintering onions.

Plot 2: Root crops such as carrots, parsnips and beetroot, parsley (closely related to carrots and parsnips), plus spinach, chicory, endive, chard, lettuce, sweetcorn. In winter – grazing rye or phacelia.

Plot 3: All the brassicas including summer and winter cabbage, sprouts, kale, calabrese, kohl rabi, swede, oriental cabbage, turnips, radish, mustard as a green manure. In winter – winter greens.

Plot 4: All onions including garlic and leeks, plus peas and beans. In winter – winter tares.

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