Invasive plants common in gardens
A large number of garden plants are current or potential environmental weeds, and often cause problems in domestic situations, too. Listed below are some of the most problematic, together with methods of eradicating them from gardens.
Please note:
- Where herbicide is suggested, nursery and garden centre staff can recommend the most suitable product for a particular plant. Always read the label before using.
- Where felling of a tree is suggested, it is recommended to employ a tree removal specialist who has the proper equipment and insurance.
- Where digging or pulling out plants is suggested, dispose of them responsibly by recycling through a local council collection service or taking them to the tip.
Arum lily
All parts of the arum lily (Zantedeschia aethiopica) are toxic. Poisoning symptoms include swelling and burning of lips, tongue and throat, stomach pain and diarrhoea. According to Australian hospital records, arum lily causes a significant number of child poisonings. It is also harmful to pets and livestock.
Arum lily is a now Declared Plant for the whole State of Western Australia. Since 1 September 2006, it has been illegal to sell or trade arum lily plants, seeds or tubers. However cut flowers can still be sold.
Arum lily has already invaded thousands of hectares of pasture paddocks, forest and wetland throughout the south-west and is still spreading, despite the efforts of community groups and landholders.
Although vegetative spread is slow, arum lily produces many berries (each containing four to five seeds), which are dispersed by birds or water. Arum lily forms dense monocultures. Gardeners who want to keep growing it should cut off the seed-heads before they mature. This way, the flowers can be enjoyed without allowing the plant to reproduce.
There are two ways to eradicate arum lily from the garden. It can be dug out, although with large clumps this is hard work, and any small daughter rhizomes left behind will produce new plants. Herbicide like glyphosate is effective when applied between June and September, but a follow-up application may be necessary after a year or two.
Blue periwinkle
Blue periwinkle (Vinca major) has invaded shady sites, including creeklines and woodlands, from Perth to Albany. In the garden its rampant growth can become a big problem because the trailing stems can take root wherever they touch the ground.
Eradicating it from the garden is hard. Herbicides like glyphosate only work when used at very high rates and with a wetting agent. Once the blue periwinkle is dead, it can be pulled or dug out.