Pyrethrum

Pyrethrum
Tanacetum cinerariifolium Syn. cinerariifolium

Pyrethrum is a perennial herb that grows to about 30cm. It has grey hairy leaves that are fine and deeply divided. Flowers are solitary and grow on long stems. Flowers are daisy like with a yellow centre and white ray petals.

Pyrethrum is a broad-spectrum spray which will kill a large number of pests, is relatively harmless to mammals and breaks down in sunlight within about 24 hours.

It kills all sap-sucking insects and will also affect grasshoppers, beetles and caterpillars. Pyrethrum should be used later in the day so bees aren’t affected.

Although Pyrethrum is not very solvable in water a mild spray can be made by infusing a half a cup of flowers into a litre of boiling water. When cool add a small amount of pure soap, shake well and spray on plants.

A more effective spray can be made by covering flowers in alcohol such as brandy or vodka and leaving for a couple of days in a dark place. Use by straining off liquid and adding 6 parts water to 1 part concentrate. Use immediately.

Growing Conditions

Pyrethrum prefers an open sunny position with well drained soil. It likes good air movement around it and doesn’t like to be overgrown by other plants. Plants can be divided in autumn to produce more plants.