 The pungent odour of onions, leeks and chives help repel the carrot root fly, and other vegetables that team well with carrots include lettuce, tomatoes and radishes, as well as the herbs rosemary and sage.Carrots thrive in the presence of caraway, coriander, chamomile, marigold and Swan River daisy.They can also be good companions for other plants; if left to flower, the carrot, like any umbellifer, attracts predatory wasps that kill many garden pests.