African feathergrass

Pennisetum macrourum is a robust, perennial grass that grows up to 2m tall. The strong creeping rhizomes it produces help it to form dense clumps which can resemble the more common pampas grass. The seed heads are narrow and up to 300mm long, whereas those of pampas are larger and have a more fluffy appearance. This species can become a serious weed of pasture, roadsides, stream banks, wasteland and urban amenity areas.

Bathurst bur

Xanthium sfrinosum is an annual that grows up to 1m tall. The stems are greenish-yellow. At the base of each leaf stalk and stem node are one or two 3-pronged yellow spines. Leaves are dark green and shiny with a white mid rib. The seeds (burs) have tiny hooked spines that allow them to cling to wool, clothing and other fibrous material. This species is a serious weed of sheep and crop farms because the burs can damage shearing equipment and irritate shearers' skin and the spines can damage the feet of livestock. Infestations can compete strongly with summer crops and burs may contaminate seed lines.

Blue Passion flower

Passiflora caerulea is a vine that can grow up to ten metres high, with tendrils allowing it to cling to host plants or supporting structures. The shiny leaves are usually five-fingered. The attractive flowers appear from December to April and are up to 10cm in diameter. Flowers are followed by egg-sized, deep-orange fruits. Birds and possums feed on these fruit and spread the seeds.

The vine grows on bush margins, scrub and in urban situations. It can smother and damage native vegetation, and prevent regeneration.

Eel grass

Vallisneria is an aquatic species originally introduced for aquariums. It has long, strap-like green leaves which can grow up to 5.5 metres long and 0.4-8cm wide. Numerous roots, up to 40cm long, sprout at each leaf-bearing node. It spreads by rhizome fragments that break off in floods and establish wherever they settle.

Eelgrass can grow in depths of up to nine metres in either still or flowing water. It crowds out native aquatics and forms dense vegetation. It also reduces water flow, causing flooding, silting and restricting recreational activities.

Manchurian wild rice

Zizania is a very tall wetland grass, reaching heights of four metres. The leaves are usually erect but may bend over at the top without twisting, unlike the leaves of raupo, which twist. Flowers are 40-60cm long and purplish or red-brown. The seeds are produced in December and germinate very quickly. This grass has deep roots and thick rhizomes which break off and are carried by water to new sites.

Manchurian wild rice is an aggressive coloniser of wetland areas and has the potential to invade both freshwater and saline wetlands.

Climbing spindle berry

Celastrus orbiculatus is an aggressive, scrambling climber, also known as Oriental bittersweet. Young twigs often have sharp spines. l-2mm long. It has pale-green leaves arranged alternately on the stem that turn yellow before falling in autumn. The small, green flowers are followed by vibrant red and yellow fruit. Birds eat the food and spread the seeds.

This invasive vine quickly strangles its host plant and its layering stems can form impenetrable thickets. It will invade bush, scrub and bush margins.

Mignonette (Maderia) vine, Anredera ordifolia

This scrambling, fast-growing climber has bright green, very fleshy, heart-shaped leaves and red / green stems. Numerous small, creamy-white fragrant flowers hang in slender spikes about 18cm long. The plant reproduces by irregular wart-shaped tubers growing from both the stems and underground.

The vines rapidly invade the canopy where the heavy growth smothers and displaces other species. It can quickly become the dominant vegetation of an area and poses a series threat to native vegetation.

Moth plant, Araujia sericifera

Also known as kapok plant. This scrambling climber grows up to six metres high. The lance-shaped leaves are dark-green on the upper surface and whitish-green beneath. The small, white flowers have five petals. The large pear-shaped fruit is grey-green and contains hundreds of fluffy white seeds, which are easily dispersed by wind when the fruit spits open. The vine produces a milky-white sap when damaged.

The dense growth smothers host plants and the heavy weight of fruiting vines can cause collapse of limbs and smaller trees.

Perennial nettle, Urtica dioica

Perennial nettle is an erect plant growing up to 1.5 metres tall. Serrated leaves are up to 10cm long and covered in stinging bristles. Small green flowers hang in tassels up to 3cm long. Perennial nettle forms rhizomes which can spread 2.5m in a season.

This plant is often found in damp situations or in areas where stock congregate. It is unpalatable to stock and can form dense clumps.

Saffron thistle, Carthamus lanatus

A rigid, annual or biennial which can grow more than a metre high. It produces one yellow flower on the stem from January to April, and has glossy, dark-green leaves.

Found in arable areas and pasture, saffron thistle is an aggressive invader particularly where there is poor pasture competition. It can cause injury to stock and devalue their fibre and heavy infestations can prevent stock movement.

Smilax (Asparagus asparagoides)

Also known as bridal creeper, this attractive climber has multiple-twining stems growing from tuberous roots attached to rhizomes. It has shiny-green foliage, small (10mm diameter) flowers in winter-early spring and red berries in early summer. Smilax can be dormant in the warmer months, with foliage dying back over summer and growing again over winter. It is spread by birds and the plant's rhizomes.

This invasive shade-tolerant creeper can eliminate all shrubs and ground layer plants, and prevent regeneration of canopy species.

Sweet pea shrub (Polygala myrtifolia)

Sweet pea shrub is an attractive bush that can grow to two metres high. The pea-like flowers are produced all year except for a short period during summer. Its petals are pinky-purple and streaked green on the outside of the flower. Seedlings generally occur close to the parent plant.

Sweet pea shrub can drastically alter the ecology of coastal areas, establishing on coastal bluffs and shrublands, as well as invading forest margins and preventing regeneration of native seedlings.

Note: Two seedless varieties are popular among gardeners (Polygala myrtifolia var. grandifitlia and Polygala x dalmaisiana). These plants do not need to be destroyed.

Woolly nightshade (Solanum mauritianum)

Woolly nightshade is an aggressive, fast-growing shrub or small tree that can reach up to nine metres in height. The large, velvety leaves are grey-green on the upper surface and white to yellowish-green underneath. It has mauve flowers throughout the year and clusters of dull, yellow, round berries. Each berry contains many seeds.

It is an invasive species that can form colonies and suppress regeneration of native species. It can invade pastoral and horticultural land and may poison livestock. Some people may have an allergic reaction to the fine dust produced by the leaves.