Onions can be grown easily either indoors in containers or outdoors. It helps in growth of fruit trees, nightshades (tomatoes, peppers, potatoes), brassicas, carrots and repels slugs, aphids, carrot fly, cabbage worms. They should not be planted along with beans, peas and parsley.You can harvest onions at any stage. The plants you thin from a row can be used as green onions. However, they are ready when about ½ the tops have fallen over and the bulbs’ skins have a papery feel.