How to maintain agapanthus, arum lilies

Research indicates about 65 per cent of weeds introduced into the environment are the result of having escaped from parks and gardens.

So, what makes an aesthetically pleasing, harmless looking plant a potential environmental thug? The key lies in the plant's ability to adapt to localised climatic and soil conditions.

The agapanthus, commonly known as Lily of the Nile, has become synonymous with the summer garden. However, the perennial has fallen from grace as it produces copious seeds that readily germinate, making them a potential environmental weed in some regions.

This characteristic of agapanthus is simply a plant management issue. The responsible gardener only needs to prune off spent flower heads before they set seed to prevent agapanthus becoming a problem.

Dwarf agapanthus is ideal for rockeries or containers and, just like the taller forms, is spectacular when planted in drifts along driveways or around swimming pools. The classic blue or white agapanthus is now supported by deep indigo in the variety Black Pantha and bicolour varieties such as Queen Mum and Cloudy Days.

The softer tones of blue and white have raised the stature of agapanthus.

Another plant that has become maligned due its weedy status is zantadeschia. Commonly known as the arum or calla lily, it is not a true lily.

Cut flowers of arums last well in a vase, but if left on the plant it will produce seeds that germinate readily, particularly along creeks and streams, potentially choking the waterways.

The variety Green Goddess also displays this weedy characteristic, so regularly remove spent flowers.

The dramatic increase in the use of water-wise exotic plant species, particularly ornamental grasses and tufting perennials, pose potential threats as environmental weeds, especially in areas close to natural vegetation zones.

The use of drought-hardy exotic grasses and perennials is one way of improving water efficiency in gardens. Such plants could be the catalyst for future environmental problems.

Managing plants is a part of responsible gardening. With a little research and understanding, gardeners can enjoy the best of all plants.