Planting partnerships to avoid

I was unaware of this as well Mamzie, but apparently marigolds give off a chemical that suppresses growth in some plants especially brassica and beans, the effect is called allelopathy and though the effect can stay in the soil for up to a year but adding compost to the soil increases the biological activity which will break down the chemical, you could ofcourse grow marigolds in pots close to the beans etc. as it's the roots which give out the chemical