Which Plants Should Grow Together? Companion Planting Guide

Some plants help each other along, some quietly hold each other back, and the rules are easy to get wrong. List what you are growing this season and this tells you the ideal neighbours for each and why, the combinations to keep apart and the reason, which flowers and herbs pull in pollinators or push off pests, and how to arrange it all in the bed.

I'm planning to grow {main_crops} (e.g. tomatoes, courgettes, beans) in my garden this season. Using companion planting principles, tell me: which plants make ideal neighbours for each of my chosen crops and why, which combinations I must avoid and the reason for each conflict, which companion flowers or herbs would help with pest control and pollination, and how to physically arrange companions in a bed for maximum benefit. Where the science is well-established cite the mechanism (e.g. nitrogen fixing, volatile compound release); where it's more folkloric, say so honestly. Finish with a simple companion planting table I can pin up in the shed.