Why does the cabbage in its third year on the same spot grow only poorly, though you do everything as always? Because the soil is one-sidedly exhausted and diseases and pests of that plant family have built up in the bed. That is exactly what crop rotation prevents.
It sounds like farming and big fields, but it matters just as much in the smallest vegetable garden. And it follows only two rules that are easy to remember. Follow them and you harvest more, feed less and struggle far less often with problems.
Why crop rotation matters so much
Every plant family draws certain nutrients especially hard and leaves behind a one-sidedly emptied soil. Grow the same family again and again in the same place and exactly what it needs most is missing, while other things remain in excess.
The second point weighs even heavier: soil-borne diseases and pests build up. Clubroot in brassicas or nematodes stay in the soil for years and hit the next plant of the same family all the harder. A change denies them the host plant and lets the pressure drop.
Rule 1: The feeder order
Sort your crops by their hunger. That way you pass the nutrient store of a freshly fed bed sensibly through several years, instead of wasting it.
From heavy feeder to recovery
- Heavy feeders (year 1)
Brassicas, tomato, cucumber, squash, courgette, potato, celery and leek. They go on the bed freshly supplied with ripe compost.
- Medium feeders (year 2)
Carrot, beetroot, onion, fennel, lettuce, chard and kohlrabi. They live off the remains the heavy feeders left behind.
- Light feeders (year 3)
Herbs, radish, lamb's lettuce and above all the legumes like pea and bean. They get by on little and even give something back.
- Green manure (year 4)
Instead of a harvest you grant the bed a restorative green manure of phacelia, clover or legumes. It builds humus and prepares the next cycle.
Rule 2: Keep an eye on the plant families
The feeder order alone is not enough, because many diseases are tied to a whole family. So the rule is: a family returns to the same bed only after three to four years at the earliest.
The four-field plan
The easiest way to do both is a four-field plan. You divide your vegetable garden into four sections as equal as possible. Each is used differently for a year and then moves one stage on.
Field 1: heavy feeders
Here goes the ripe compost, and on it you plant the hungry heavy feeders like cabbage, tomato or squash.
Field 2: medium feeders
Onto last year's bed, without fresh full feeding, move the medium feeders like carrot, onion or lettuce.
Field 3: light feeders and legumes
Now come light feeders and legumes. The beans and peas enrich the soil with nitrogen for the next round.
Field 4: green manure
The fourth bed recovers under a green manure. Next year everything moves on a stage, and field 4 becomes the freshly fed heavy-feeder bed again.
No feeder and no family twice in a row in the same place. Whoever rotates harvests more and feeds less.
The core rule of crop rotation
Frequently asked questions
How long must I pause with a family?
As a rule of thumb, three to four years. Only then does the cabbage or the tomato, for example, return to the same bed. With stubborn soil diseases like clubroot, the pause may be longer.
Does crop rotation apply in raised beds and pots too?
Yes. In the limited volume of a raised bed or pot especially, a crop exhausts the soil one-sidedly fast. Change the crop yearly or replace part of the soil in the pot.
Why are beans and peas so valuable in the rotation?
Because through nodule bacteria on the roots they fix airborne nitrogen and enrich the soil, instead of draining it. After them even a hungry heavy feeder thrives. They are the ideal preceding crop.
What is the difference between crop rotation and mixed cropping?
Crop rotation governs the succession over the years, mixed cropping the side-by-side in the same season. The two complement each other. More on it in Mixed cropping: good neighbours.
I only have a small bed. How do I do crop rotation?
Even a single bed can be divided in your mind into sections that rotate yearly. What matters above all is to keep the families apart and not set heavy feeders like tomato or cabbage in the same spot every year.
