Pyrethrum

Chrysanthemum cinerariifolium

Because of the natural insecticidal properties of the pyrethrums, they are used as companion plants, to repel pest insects from nearby crops. One might, for instance, plant them among broccoli plants in order to protect them from any of several insect pests. They are thought to repel aphids, leafhoppers, spider mites, harlequin bugs, ticks.