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Waterway Weeds

Chemical control should be carried out by a licensed professional. Please contact the CCG office for more information.

The following weeds are commonly found in and around the waterways of the SW.

Arum Lily, Zantedeschia aethiopica

Introduced from South Africa as a garden plant, it has since become an established weed. It is found in creeks, ditches and damper areas of the SW area. It often occurs in large stands, giving almost 100% cover in the worst scenarios. The plant germinates in and starts flowering in early winter, then sets seed before dying back in the summer months. The plant spreads rapidly via its seeds which are very palatable to birds and through its vegetative root system.

Control is through the use of chlorsulfuron in winter and spring.

Blackberry, Rubus sp.

Native to Europe, Blackberry is a Weed of National Significance. It spreads via seeds, suckers and the rooting of cane tips. The fruits are very attractive to birds and mammals, especially foxes, which may transport the seeds large distances. Large stands can quickly develop which become impenetrable over time. Blackberry can be controlled by spraying with metsulfuron in the dry summer months.

Kikuyu, Pennisetum clandestinum

Kikuyu is a perennial ground-hugging grass which spreads via runners. It is often found along creeklines which run through paddocks and is recognised as a weed in WA. Glyphosate can be used to control this weed, though it is difficult to eradicate completely due to its runners.

Watsonia, Watsonia bulbilifera

Originally introduced as a garden ornamental, W. bulbilifera is now a serious weed of roadsides and disturbed areas. It grows readily in the south west, especially in damper areas where it crowds out native species.

The manual removal of watsonia can be effective where isolated plants occur within good bushland, otherwise chemical control with Glyphosate in spring is recommended. The dilution used will depend on the risk of off-target damage to native vegetation.

Juncus microcephalus

A robust perennial, J. microcephalus occurs in disturbed wetlands and rivers. It is a rapid coloniser of silt beds and riparian zones which leads to changes in water flow, increased erosion and sedimentation. Mature plants release a large amount of seed. Treatment is with 2% Glyphosate + wetting agent in late summer / autumn if there is surface water throughout the year. In dry conditions apply in spring / early summer.

Edible fig, Ficus carica

The edible fig is native to southwest Asia and is widely grown for its fruit. It is one of the first plants to be cultivated by humans, first recorded in southern Arabia in 2900BC

Hand-pull seedlings; Cut and paint large trees with 50% – 100% Glyphosate. Saw or lop tree as close to ground as possible. Essential to apply herbicide immediately to cut trunk with spray, brush, wick or squirt bottle

Sweet Pittosporum, Pittosporum undulatum

This sub-tropical tree is native to eastern Australia but has become a problem species both within and outside its natural range. Pittosporum is an evergreen tree, growing to around 14m and has bright orange fruit. Originally introduced to WA as a garden plant it is now prevalent in bushland areas. Pittosporum is very adaptable. It shades out other vegetation and changes the soil nutrient load with increased leaf litter. Seeds are spread through the activity of birds and animals and the dumping of garden waste. Small saplings can be hand pulled but the roots must dry out to prevent the plant re-rooting. Larger trees can be cut at ground level and the stump painted with 100% glyphosate. Adult Pittosporum trees are destroyed by fire.

Sydney golden wattle, Acacia longifolia

Sydney golden wattle is a highly invasive and destructive weedy wattle. It is spreading widely and readily into undisturbed bushland as well as degraded sites.  

Hand-pull seedlings; Fell mature plants as close to ground as possible.

Basal bark – useful on stems less than 20cm diameter. Spray or paint lower 60cm of bark with herbicide, picloram/triclopyr, and penetrant (usually diesel)

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