The two most useful of these plants are P. parthenium, known as feverfew or bachelors buttons, used as an edging or carpet bedding plant, and P. roseum the forerunner of the lovely herbaceous pyrethrums so prized by gardeners for their beauty as decorative garden plants and cut flowers.

All pyrethrums are easy to cultivate, especially the large flowered types as they grow well in most garden conditions and, if lifted and divided every second year, will grow and flower well.

They have a long flowering period commencing in spring and often continue through to the autumn. 

An insecticide widely used today is made from the flowers of P. cinerarifolium, a plant native to Austria.  The white flowers contain six chemical compounds known as pyrethrins, which when combined form the broad spectrum insecticide known as pyrethrum.  

Pyrethrum disrupts the central nervous system of sap-sucking insects causing their nerve impulses to shut down which leads to their eventual demise.   

Pyrethrum roseum was also used in a similar way but proved not so effective. It used to be sold as Persian Insect Powder when I was a child. When used as a flea powder on dogs, the fleas would leap off in a frenzied evacuation. 

Pyrethrums are often used in the garden as companion plants to repel insects pests from around vegetables and ornamental plants. 

Geraniums should be giving an abundance of beautiful blooms and in order to keep them flowering it is necessary to give the plants a little attention. 

Give the soil around the plants a good hoeing because this will open the soil allowing air to penetrate into it. This hoeing stops the soil from becoming stale and reduces the need to water as much.

Geraniums are brilliant in that they are not generally susceptible to the array of pests which attack many other plants. In fact, this adds to the pleasure of cultivating these darling plants.

During this month some geraniums may develop dry yellow leaves which show signs of rust. This is a common complaint and with a little care we can help the plants with this problem.

First of all remove all the affected leaves and immediately bag them and put into the rubbish bin.  Don’t leave the affected leaves on the ground around the garden.

To control rust use a suitable fungicide and spray the plants according to the directions. Do this once every two weeks and you should find that after three applications new leaves will appear and the plants will look much healthier.

The idea that a geranium will grow well in poor soil is not so. The best plants are those growing in beds or containers where they have had some fertiliser and well-rotted compost added. 

Grown in poor soil geraniums produce stunted growth with pale leaves and very little flowers instead of healthy green leaves and the abundance of brightly coloured flowers we all admire.

January 26, 27:  North-West Tasmanian Lilium Society Latrobe Lilium Show, Memorial Hall, Gilbert St. Saturday 1pm-4pm, Sunday 10am-4pm. Bulbs, plant and seed sales, demos, flower auction Sunday 4pm.  Admission $4. Accompanied children free.

February 2,3:  The Launceston Horticultural Society’s Summer Show features dahlias, begonias, liliums and gladioli.  Saturday 2pm-5pm and Sunday 10am-4pm.  Displays of cacti and succulents also delphiniums and begonias. Specialists plant growers, cut flowers, floral art, children’s exhibits, refreshments.  Admission $3 adults.