Plant · P-129

Pyrethrum Daisy

Tanacetum cinerariifolium

Pyrethrum daisy is the source of pyrethrin, the natural insecticide extracted from its yellow disc florets at full bloom, and it is genuinely broad-spectrum - killing beneficial insects along with pests, which is why growers spray it in the evening so it breaks down before morning. It cannot handle sustained daytime heat above the mid-90s F paired with warm nights: a University of Arizona trial planting vigorous transplants in irrigated desert lost over 99 percent of them to heat and crown rot in a single summer, and even where it survives, heat during flowering weakens both flower yield and pyrethrin content. It offers no food value and only minor medicinal use, so the insecticide is the only reason to grow it - and where the climate won't support it, buying the extracted pyrethrin is more realistic than farming the plant.