James Whitaker
Why crop rotation is worth the effort
If you've ever grown cabbages in the same spot for three years running, you'll know the signs: stunted plants, yellowing leaves, and a soil that seems to have lost its get-up-and-go. Crop rotation is the allotment keeper's oldest trick for avoiding that slow decline. By moving your crops around each year, you stop pests and diseases building up in the soil, and you give each plant family the nutrients it needs without exhausting your plot. It's not complicated, and on a small plot it's even more important, because you can't afford to let a bed go bad.
The four main crop groups
Most rotation plans divide vegetables into four families. Each has its own habits, so grouping them makes sense.
- Legumes – peas, broad beans, runner beans, French beans. They fix nitrogen from the air into little nodules on their roots, leaving the soil richer for whatever follows.
- Brassicas – cabbages, kale, broccoli, sprouts, swedes, turnips, radishes. They are hungry plants that love nitrogen and need a firm, lime-rich soil to avoid clubroot.
- Roots – carrots, parsnips, beetroot, onions, garlic, leeks. They cope with less rich soil and actually fork or split if given fresh manure. They also struggle if nitrogen is too high.
- Potatoes and the rest – potatoes, tomatoes, peppers, courgettes, sweetcorn, salad leaves. This is a mixed bag, but potatoes are the classic headliner. They need plenty of organic matter and their dense foliage helps smother weeds.
Your simple four-year rotation plan
If you have four beds or can split your plot into four roughly equal sections, here's the rotation to follow. Write it down or draw a little map, because next spring you'll be glad you did.
- Year 1: Bed A – legumes. Bed B – brassicas. Bed C – roots. Bed D – potatoes.
- Year 2: Move everything on one. Bed A – brassicas. Bed B – roots. Bed C – potatoes. Bed D – legumes.
- Year 3: Bed A – roots. Bed B – potatoes. Bed C – legumes. Bed D – brassicas.
- Year 4: Bed A – potatoes. Bed B – legumes. Bed C – brassicas. Bed D – roots.
Then start again. The beauty is that legumes always precede brassicas, giving them a nitrogen boost. Brassicas then get lime in winter if your soil is acidic. Roots follow brassicas, and because brassicas were harvested by autumn, you can leave the soil to settle over winter – perfect for carrots. Potatoes come last, and you can pile on well-rotted manure in autumn before planting. After potatoes, the soil is clean and ready for legumes again.
Adapting rotation for raised beds and tiny plots
Not everyone has four neat beds. On a half-plot or a collection of raised beds, you can still rotate. If you have three beds, group potatoes with roots one year, then swap. Or use large containers for hungry crops like courgettes and tomatoes, and rotate the rest. The key is to never follow a crop with another from the same family. So don't plant tomatoes where potatoes grew last year, and don't follow cabbages with kale. Keep a notebook – even a simple list on your phone – and note what grew where. That record is your best tool.
Feeding the soil as you rotate
Rotation is not just about pests. It's also about matching hungry crops to rich soil and lighter feeders to poorer soil. Add compost or well-rotted manure to the potato bed in autumn. Lime the brassica bed in winter if you know your soil is acidic – but never lime before potatoes, as it encourages scab. For roots, add a light dusting of wood ash if you have it, but skip fresh manure. And consider sowing a green manure like field beans or grazing rye on any empty bed over winter. It protects the soil from rain and weeds, and you dig it in come spring. That's free fertility, and your worms will thank you.
Common pitfalls and how to dodge them
The most common mistake is losing track. By July, everything looks green and you've forgotten which bed had the onions. So label your beds, or take a photo. Another pitfall is planting perennial crops like rhubarb, asparagus, or Jerusalem artichokes in the rotation – give them a permanent spot instead. Don't panic if your rotation slips a year; just do your best next season. And remember that crop rotation works best alongside good hygiene: clear old leaves, don't compost diseased brassica stems, and wash your tools. On a small plot, a little planning goes a long way. Stick with it, and you'll be harvesting healthy crops for years to come.
