At least 1 m²11 ft². If your bed is smaller, the planner grays this plant team out, says why, and offers the nearest adaptation that fits. It never swaps in something else without telling you.
What it looks like planted
5 × Carrot
5 × Chives
5 × Lettuce
The real placement on an example 4 ft bed, the same layout the planner draws.
Between seasons
Living perennials stay in the bed between seasons, so only part of the ground gets rotated.
What it claims
Alliums interplanted with carrots reduce carrot rust fly damage
How it works: The carrot rust fly finds its host by the smell of carrot foliage. Onion and other allium volatiles growing among the carrots mask that scent, so fewer flies locate the row to lay eggs. Because the protection is the smell, it lasts only while the alliums are in the ground. Once they are pulled, the masking goes with them.
Evidence: checked against 1 source in the research-based literature.
How it works: A living cover keeps a leaf canopy over the ground. It intercepts light at the soil surface, so weed seedlings are shaded out before they establish, and it slows surface evaporation, so the soil holds more water. In a Three Sisters planting this is the squash's role. Its broad leaves shade the bed.
Evidence: checked against 2 sources in the research-based literature.
If you skip this, you lose real yield. The planner warns you.
How it works: Soilborne inoculum and overwintering pest stages disperse across the bed. A plant team dominated by one family forecloses that ground for that family's rotation interval.
Evidence: checked against 2 sources in the research-based literature.
Remedy
Rotate the whole bed the plant team occupied, including rows that family never grew in.
