A cut above the rust

The Age

Saturday February 19, 2011

BY DENISE GADD

A FRIEND rang me recently lamenting the fact that there was rust on the leaves of her prized geraniums. Humidity is the problem, I told her. The same with black spot on roses, tomatoes growing like crazy but hardly fruiting, blighted azaleas and bugs eating everything. It all comes down to the recent humidity.As far as my friend's geraniums are concerned, all she can do is spray and remove the badly infected foliage (disposing of it in the rubbish bin, not the compost). It's also good to leave some space around the plants to allow the air to move freely so they can dry out, as they hate being wet. Regal pelargoniums get a green virus that also needs spraying. Getting rid of the affected leaves is also paramount.Janine Kay from the Australian Pelargonium and Geranium Society says when the plants contract rust or green virus, it's the botanic version of catching a cold. "Many of the plants are affected this year because they're stressed after years of drought, then we've had all this water and humidity. They hate it."And this brings me to the question, when is a geranium not a geranium? There is often confusion surrounding its botanic identity. Is it a geranium or is it a pelargonium? Plants often called geraniums are actually part of the pelargonium genus. While both are in the same family (Geraniaceae) geraniums are commonly known as cranesbills ��� from the Greek word geranos, meaning crane ��� and form a different group of about 300 species of perennials and subshrubs.Geraniums usually have palmate leaves, so called because they resemble an open hand, bloom profusely over summer and also have five-petalled flowers in pink and purple shades.The foliage is often scented and the oil it produces is used in aromatherapy and beauty products.Pelargoniums, on the other hand, are commonly known as storkbills (the name comes from the Greek pelargos meaning stork, which refers to the shape of the seed pod) and the group comprises about 250 perennials, annuals and shrubs. Foliage varies but is often light green, rounded or hand-shaped and some have succulent leaves.The flowers are made up of five petals and are often brightly coloured, providing a spectacular show at this time of year.But what's the difference between regal and zonal pelargoniums, I hear you ask. Well, zonal pelargoniums ��� or to give them their botanic name Pelargonium x hortorum ��� are commonly called geraniums. Flowers come in single, double and semi-double forms and often feature spots and stripes. Varieties include the coloured-leaf zonals that are more often grown for their fancy foliage than their flowers and which come in to their own in cooler weather.The staphs have small star-shaped flowers and the ivy-leaf geranium is a common sight growing from hanging baskets and window boxes in the south of France and Italy. Species pelargoniums differ totally from an ordinary pelargonium and often have succulent-type leaves and very small flowers.Regal pelargoniums (Pelargonium x domesticum) produce showy azalea-type flowers from spring to autumn and the leaves have a serrated edge. There are also regal or angel varieties. They are easy to grow and keep producing flowers in season when deadheaded regularly.With her mother Shirley Stockley president of the APGS and father Michael its treasurer, it was a inevitable that Kay would fall in love with these rewarding and tough plants. The society's editor of its newsletter and manager of the spring and autumn shows, Kay grows hundreds of zonal and regal pelargoniums. ""Now I have a bigger collection than mum. There are lot of silly people like me. It becomes a disease but there are worse things you can do."

© 2011 The Age

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