Environmental Weeds in South Australia
Environmental weeds degrade our natural landscape, generally by reducing biodiversity. Direct impacts occur when weeds out-compete native vegetation for water, light, or soil nutrients. Indirectly environmental weeds can:
- Cause loss of food sources and habitat for wildlife.
- Provide shelter for feral animals that prey on native wildlife.
- Change soil or water nutrient loads, affecting native plant growth.
- Alter fire intensity and frequency, which in turn affects native plants and animals.
- Disrupt water flow patterns and cause erosion.
Many weeds begin as garden plants. Be aware when buying garden plants that some species can spread into the bush.
Environmental weeds of concern include:
African boxthorn (Lycium ferocissimum), Aleppo pine (Pinus halepensis), Blackberry (Rubus fruticosus), Boneseed (Chrysanthemoides monilifera subsp. Monilifera), Bridal creeper (Asparagus asparagoides), Buckthorn (Rhamnus), Bulbil watsonia (Watsonia meriana var. bulbillifera), Buffel grass (Cenchrus ciliaris), Cape broom (Genista monspessullana), Cape tulip (Moraea flaccida and Moraea miniata), Desert ash (Fraxinus angustifolia subsp. Angustifolia), Dog rose (Rosa canina), Fountain grass (Pennisetum setaceum), Gazania (Gazania spp.), Gorse (Ulex europaeus), Hawthorn (Crataegus monogyna), Mirror bush (Coprosma repens), Native bluebell (Billardiera fusiformis), Olives (Olea europaea ), Polygala (Polygala myrtifolia),, Pussytail grass (Pentaschistis pallida), Sweet pittosporum (Pittosporum undulatum), and Willow (Salix spp).
How do native plants become weeds?
Most of our weeds are introduced from overseas, but some are Australian native plants that are growing outside of their natural or pre-European range. Just like their exotic counterparts, these plants become weedy when they encounter a new environment that lacks the usual herbivores, fungal diseases, insects or climatic constraints that keep them in check.
Many of these have escaped from gardens, but some have spread from ill-conceived revegetation projects, such as windbreaks or shelter belts. In SA the most common group of natives to go weedy is the wattles, but also Hakeas, Grevilleas and Eucalypts.