Crop Rotation

Rotation is about what grew in a bed in previous seasons. Companion planting is about plants growing together now. The planner keeps them separate, and so should you.

What rotation does, and does not do

Many soil-borne diseases and some pests survive between seasons in soil, crop debris and volunteers: late blight and wilts in nightshades, clubroot in brassicas (for a decade or more), white rot in onions, root rots in legumes. Growing the same family in the same bed year after year lets those organisms build up. Moving the family to a different bed for two to four years interrupts the cycle. That is the whole of the evidence-based case for rotation; it does not make plants "friends" and it says nothing about which plants should sit next to each other this summer.

Rotation also balances fertility (heavy feeders after legumes) and root depths, but those are second-order benefits in a home garden where compost is added every year.

How the planner uses bed history

You record what grew in each bed in previous seasons (or import last year's plan).
When you place a crop, the planner checks its family against the bed's history and the family's rotation interval.
A conflict appears as a rotation warning with the named risk, on its own layer, never as a companion conflict.

Rotation warning, not a companion conflict: both crops belong to the same family and may share certain soil-borne disease risks across seasons. They are not automatically poor neighbours in the current season.

A four-bed, four-year example

Bed	Year 1	Year 2	Year 3	Year 4
Bed 1	Nightshade family	Legume family	Cabbage family	Carrot family
Bed 2	Legume family	Cabbage family	Carrot family	Nightshade family
Bed 3	Cabbage family	Carrot family	Nightshade family	Legume family
Bed 4	Carrot family	Nightshade family	Legume family	Cabbage family

Cucurbits and alliums fit into a 5- or 6-bed cycle; in fewer beds, alternate families within a bed and keep the longest gaps for brassicas (clubroot) and alliums (white rot).

Plant families in the catalog

Solanaceae Nightshade familyTomato, Pepper, Eggplant, Potato 3-year gap · late blight (Phytophthora infestans), early blight Brassicaceae Cabbage familyCabbage, Broccoli, Cauliflower, Kale, Brussels sprouts +8 3-year gap · clubroot, cabbage root fly Fabaceae Legume familyBush beans, Pole beans, Peas, White clover 2-year gap · root rots (Fusarium, Pythium), bean rust Cucurbitaceae Squash familyCucumber, Zucchini, Winter squash, Pumpkin, Melon 2-year gap · powdery mildew, bacterial wilt Apiaceae Carrot familyCarrot, Parsnip, Celery, Parsley, Cilantro +2 2-year gap · carrot rust fly, Alternaria leaf blight Asteraceae Daisy familyLettuce, Sunflower, French marigold, Calendula, Cosmos 1-year gap · lettuce downy mildew, aphids Amaryllidaceae Onion familyOnion, Garlic, Leek, Chives 3-year gap · onion white rot, downy mildew Lamiaceae Mint familyBasil, Rosemary, Thyme, Oregano, Sage +2 1-year gap · downy mildew (basil), root rot in wet soil Amaranthaceae Beet familyBeet, Swiss chard, Spinach 2-year gap · leaf miner (Pegomya), Cercospora leaf spot Poaceae Grass familyCorn 2-year gap · corn earworm (also tomato fruitworm), corn smut Rosaceae Rose familyStrawberry, Raspberry 3-year gap · grey mould (Botrytis), Verticillium wilt Other familiesSingle catalog members (okra, sweet potato, asparagus, rhubarb, blueberry, nasturtium, borage, buckwheat)

**The same four beds across four seasons with plant families changing and disease-risk logic annotated.**

Small gardens

With one or two beds, full rotation is impossible. Alternatives that address the same named risks: split each bed in halves and alternate families; grow the most disease-prone families (nightshades, brassicas) in containers with fresh mix some years; remove all crop debris; choose resistant cultivars; never replant alliums where white rot appeared; and keep the bed history so the planner can show you the risk instead of hiding it.

Full rotation guide