Why rotate
- Diseases and pests. Iowa State notes that many disease organisms live in the soil and can persist there for several years. Plants in the same family tend to catch the same ones. Growing an unrelated crop breaks the cycle, because the disease or pest loses the host it needs.
- Nutrients. Different families take up nutrients in different amounts. Rotating them evens out the drain on the soil and gives it time to recover.
Which vegetables are related
Rotation works by family, not by crop, so a tomato bed shouldn't be followed by capsicums or potatoes. The main vegetable families, following Iowa State's list, with the names used in Australia and New Zealand:
| Family | Crops |
|---|---|
| Brassicas (Brassicaceae) | Broccoli, cabbage, cauliflower, Brussels sprouts, kale, bok choy and other Asian greens, radish, turnip, rocket |
| Nightshades (Solanaceae) | Tomato, capsicum, chilli, eggplant, potato |
| Cucurbits (Cucurbitaceae) | Cucumber, zucchini, pumpkin, watermelon, rockmelon |
| Legumes (Fabaceae) | Beans, peas, broad beans |
| Alliums (Amaryllidaceae) | Onion, garlic, leek, spring onion, chives |
| Carrot family (Apiaceae) | Carrot, parsnip, celery, parsley, coriander, dill |
| Beet family (Amaranthaceae) | Beetroot, silverbeet, spinach |
| Daisy family (Asteraceae) | Lettuce |
| Grass family (Poaceae) | Sweet corn |
| Morning glory family (Convolvulaceae) | Sweet potato (kūmara) |
| Mallow family (Malvaceae) | Okra |
A simple four-bed plan
Iowa State suggests three or four raised beds as the easiest way to rotate. Group the families into four sets and move each set one bed along every year:
| Bed 1 | Bed 2 | Bed 3 | Bed 4 | |
|---|---|---|---|---|
| Year 1 | Legumes | Brassicas | Nightshades and cucurbits | Roots, onions, beet family |
| Year 2 | Brassicas | Nightshades and cucurbits | Roots, onions, beet family | Legumes |
| Year 3 | Nightshades and cucurbits | Roots, onions, beet family | Legumes | Brassicas |
| Year 4 | Roots, onions, beet family | Legumes | Brassicas | Nightshades and cucurbits |
Read down a column to see one bed's sequence: legumes, then brassicas, then nightshades and cucurbits, then roots. Each family comes back to the same bed every fourth year, the gap Iowa State recommends. The traditional order puts leafy, nitrogen-hungry brassicas after legumes. Lettuce, sweet corn and herbs fit in wherever there is space, as long as they don't follow their own family.
In most of Australia a bed grows two crops a year: summer fruiting crops, then brassicas or roots through the cooler months. Rotate each season's family as well, so tomatoes don't go straight back where potatoes grew last winter. The planting calendar shows which crops go in each month in your zone.
Small gardens
- One or two beds: split each bed into sections and move the families around the sections, so the gap is as long as your space allows.
- Containers: Iowa State suggests pots and scattered pockets of garden for the crops that are hardest to move, such as tomatoes. See the pot size guide for how big they need to be.
- Plan the beds to fit: a four-bed rotation works best with four beds of about the same size. The raised bed sizes guide has the common layouts.
What rotation can't fix
Some soil-borne diseases outlast any home rotation. AUSVEG's fact sheet on clubroot, a disease of brassica roots, says the organism can persist in soil for up to 20 years. It thrives in warm, wet, acidic soil. Its management advice is to improve drainage and keep the soil pH at 7.0–7.5. The soil pH calculator works out how much lime that takes. If one family keeps failing in a bed, rotate as well as you can, and look at the soil itself too: its drainage, its pH and its organic matter.
Companion planting, growing different crops side by side, is a separate idea from rotation. The evidence for it is much patchier; see what the research shows.
Questions
Can I plant tomatoes in the same spot every year?
It's best not to. Iowa State University Extension advises waiting 3–4 years before growing the same family in one place again, and tomatoes share their family with capsicum, chilli, eggplant and potato. If you have no other spot, grow them in containers.
What should I plant after tomatoes?
Anything outside the nightshade family: roots and onions, legumes or brassicas, depending on the season. In the four-bed plan the tomato bed takes roots and onions next, and the tomatoes move to the bed that had brassicas.
How does a four-year crop rotation work?
Group the vegetables into four sets: legumes; brassicas; nightshades with cucurbits; and roots, onions and the beet family. Grow each set in its own bed and move every set one bed along each year, so no family returns to the same bed for four years.
Does crop rotation work in raised beds?
Yes. Iowa State notes that building three or four raised beds makes rotation very straightforward, with one family group per bed.
Sources
- Iowa State University Extension and Outreach, Crop rotation in the vegetable garden – vegetable families, 3–4 year gap, soil-borne diseases, nutrients, raised beds and containers.
- AUSVEG SoilWealth, Clubroot management in brassica vegetables (fact sheet, April 2024) – persistence up to 20 years, favourable conditions, drainage and pH 7.0–7.5.
Last reviewed 24 September 2026 · Report an error