Some vegetables do not grow well together and can hinder the growth of one other. If onions are grown near beans, for example, the beans' growth will be stunted. Crops that attract the same harmful bugs should also not be grown together. The secret to avoiding a potential disaster in your vegetable garden is to know which plants make ideal companion plants, and which vegetables don't grow well together.
Potatoes and Tomatoes
Potatoes and tomatoes are both in the Solanaceae family, but these vegetables do not grow well together. Do not plant these two crops next to one another because the presence of the tomato plant lowers the potato plant's individual resistance to Phytophthora infestants, commonly known as blight. This disease affects both tomato and potato plants.
Once a plant is infected, blight spreads quickly from one plant to another, and even to other gardens close by. It can wipe out entire fields, and was the cause of the Irish potato famine in 1845.
Potatoes grown near tomatoes often slow the growth of the tomato plant. When using crop rotation techniques, which means planting a crop in a different location each season, do not plant tomatoes or potatoes where the other one was the previous season.
Onions, Peas and Beans
Keep onions out of the pea and bean patch. Onions and their close relative, shallots, stunt the growth of all types of beans and peas.
If you have a small garden and wish to grow all three plants, try planting a row of beans, then a row of cabbage. Follow that with a row of onions, a row of lettuce, a row of radish then a row of peas. This way the plants are not side-by-side, and a plant that benefits both plants is growing in between them.
Cabbage and Cauliflower
Cabbage and cauliflower are not enemies. The reason these vegetables don't grow well together is that they are both affected by Plasmodiophora brassicae, commonly known as club root. This fungus causes the roots to swell up. Once this happens, the roots are no longer able to take up water. The leaves will wilt and turn yellow. The only way to deal with this is to remove the plants--roots and all.
Other vegetables that don't grow well together with cabbage and cauliflower include radish and tomato.