African tulip tree
The African tulip tree is an evergreen species indigenous to western Africa. It has been introduced throughout the tropics and is threatening biodiversity in many parts of the Pacific islands. It favours moist habitats and will grow best in sheltered tropical areas. The tree invades both abandoned agricultural land and closed forest. This species loves rich soil, but puts up with just about any type of soil.
Pinus halepensis (Pinaceae)
A coniferous tree growing up to 15m high, conical in shape with a short trunk when young and rounded to oblong with a crooked trunk when older. Crown open with silvery-grey bark becoming darker. Grey-green to yellow-green leaf needles in bundles of two 4-8cm long. It invades grasslands and fynbos, particularly on dry soils
The Algerian ash is a medium-sized, deciduous tree growing to 20-30m tall with a trunk up to 1.5m in diameter. It is not commonly planted anymore, however large numbers of adult trees can still be seen growing in suburban areas. The flowers are produced in inflorescences, which can be male, hermaphrodite or mixed male and hermaphrodite. Flowering occurs in early spring.
An erect to sprawling thorny shrub growing up to 2m high with deeply ridged stems. Green, finely serrated leaves sometimes densely grey-downy beneath. White flowers with petals that are much longer than the sepals and appear from September to January. The edible fruits are red turning black.
Triplaris americana (Polygonaceae)
This tree grows 8-10m high with a straight, smooth, grey trunk with pyramidal crown. Leaves are bright green and smooth, or brownish-velvety beneath along the midrib and veins. Small male and female flowers on separate trees from April to May in large clusters, along densely greyish-yellow, light brown hairy axes. Female flowers red. Shiny brown fruits. Poisonous leaves.
Apple of Peru
Apple of Peru is an annual shrub growing to 1m tall. It has spreading branches (the plant spreads to 1m wide) and the mid-green, toothed, wavy leaves are egg-shaped with the broad end at the base (ovate). The upward-facing flowers are most commonly pale blue and white, but there are also forms with violet or white flowers. The flowers are bell-shaped and 5cm or more across. Cherry-like, green-brown berries are encased within green or black mottled calyces. The mature fruits can resemble a lantern. The plant usually germinates in late spring or early summer.
The arsenic bush is a poisonous shrub that can grow up to 2-3m tall with yellow flowers. The leaves are arranged in pairs opposite each other, consisting of three or four pairs of ovate leaflets. The pods are cylindrical, 7-10cm long, containing shiny seeds. It is a common garden ornamental plant that also invades forest margins, savannah, riverbanks, roadsides, waste ground and plantations. It flowers from October to March.
Ash leaved maple
Acer negundo ash
Deciduous tree 10 to 20 m high with a spreading crown and often more than one trunk; bark is greenish smooth at first, aging to brown and rough. Leaves bright green, paler and sometimes densely hairy beneath, turning yellow in autumn; 3 - 9 pinnate, but mostly with 5 leaflets; leaflets coarsely toothed, 50 - 100 mm long.
This fast-growing species is particularly invasive along waterways (i.e. in riparian areas) and in sheltered forests in temperate zones, but it has the potential to invade other habitats.
Asian kelp is native to Japan where it is cultivated for human consumption. It is an opportunistic weed which spreads mainly by fouling ship hulls. It forms dense underwater forests, resulting in competition for light and space, which may lead to the exclusion or displacement of indigenous plant and animal species.
Asian wild rasberry
Rubus ellipticus is a stout evergreen shrub with prickly stem that grows approximately 4.5 metres tall. Its stems are covered with prickles and reddish hairs. It has been introduced to several places, including Hawaii, Southern USA and the UK, and is grown in cultivation for its edible fruits. This plant has become a major pest in Hawai'i, threatening its own native species of raspberry (Rubus hawaiiensis), and the ability of this plant to thrive in diverse habitat types makes it a particularly threatening invasive plant.