Check companion planting claims before I rely on them

Planning a vegetable bed and wanting to know which pairings have evidence behind them.

Assess companion planting for the crops below, separating what is supported from what is folklore.

1. **Well supported.** Pairings with a real mechanism, named: nitrogen fixing, physical shade, trap cropping, habitat for predatory insects, scent masking, ground cover suppressing weeds. Say what the mechanism is and how strong the effect actually is.
2. **Plausible but unproven.** Commonly repeated, mechanism unclear, evidence thin. Say so rather than hedging.
3. **Folklore.** Pairings with no basis, including the famous ones. Name them.
4. **Actively bad combinations**, with the reason: competition for light or water, shared pests and diseases, allelopathy, or one crop being harvested through another.
5. **A practical plan** for my bed, based only on categories 1 and 4.

Do not repeat a traditional pairing as fact because it is widely printed. Where you are uncertain about the evidence, say that.

Crops I want to grow:
Bed size and layout:
My main pest problems:

Growing food. Crops worth the space, sowing calendars worked back from frost, and pairings with real evidence.