Hairy senna

Senna hirsuta

Hairy senna is a large, upright plant with deep orange-yellow irregular flowers. The stems and leaves are covered with long, pale greyish-white hairs. The leaflets are egg-shaped and the fruit is slightly sickle-shaped. The seeds are olive or brown.


Himalayan firethorn

Pyracantha crenulata

The Himalayan firethorn is an evergreen shrub or small tree. It has spiny branches bearing simple leaves and clusters of small white flowers followed by showy red, orange or yellow berries. The leaves are hairless, have dark green upper surfaces and are glossy in appearance.


Hoary cardaria

Lepidium draba (Brassicaceae)

A densely leafy perennial reaching 90cm high with erect whitish stems and deep roots. It has small bright green, sharply toothed leaves which have a soft down on the lower half of the stem and are smooth on the upper half. Tiny white, sweetly scented flowers appear in conspicuous, dense heads from September to December. Heart-shaped fruit capsules. This plant is poisonous to livestock.


Honey locust

Gleditsia triacanthos (Fabaceae)

A deciduous, spreading tree 15-20m tall. The trunk and branches have three-branched spines. Bright green bi-pinnate leaves consist of small paired lance-shaped and minutely toothed. Small, yellowish-green flowers appear from October to November. The seed capsules are flat and twisted brown pods.


Honey mesquite

Prosopis glandulosa (Fabaceae)

Multi-stemmed acacia-like shrub or small tree up to 10m high with paired, straight spines and reddish-brown branchlets. Dark green leaves with leaflets 10-25mm long. Yellow flower spikes from June to November. Yellowish to purplish, slender, straight, woody pods. Pods poisonous and pollen is a respiratory tract irritant


Hop wattle

Acacia stricta

Erect shrub or small tree. Leaves narrow, elliptic, up to 12cm long, prominent midvein and net-venation. Flowers yellow balls held close to the stems, occurring in groups of 2-4 in the axils of the leaves, appearing in spring. Pods straight up to 100 mm long and 5 mm wide.


Horsetail tree

Casuarina equisetifolia (Casuarinaceae)

A tall evergreen tree growing up to 20-40m high with arching, slender branches. The leaves have minute scales and occur in whorls. The scales are uniformly pale with sharp ribs. This tree produces male flowers as yellowish spikes and female flowers as reddish heads from September to April, as well as small brown woody cones and winged seeds with a flattened profile


Hydrilla

Hydrilla verticillata

Hydrilla is a submerged perennial aquatic plant with branching stems up to 2m long, but in deep water can reach 7m. It forms dense submerged masses which impacts on recreational activities such as boating and fishing. It also threatens indigenous aquatic plants. It looks similar to indigenous Lagarosiphon and would need to be examined microscopically.


Hyssop loosestrife

Lythrum hyssopifolia

Hyssop loosestrife is a mostly upright, branching annual or biennial herb growing 10-60cm tall. The oval leaves are up to 3cm in length. The inflorescence is a terminal spike with pinkish petals up to 5mm long.


Imbricate prickly pear

Cylindropuntia imbricata (Cactaceae)

A spiny, much-branched succulent shrub growing up to 2m high with an erect main stem. Old branches hang downwards and the stems are dull grey-green with raised edges giving the effect of woven rope. The spines, which are up to 30mm long, are initially covered with loose, white papery sheaths. It has small leaves and showy purple-red flowers appear from November to January followed by yellow succulent fruit.