Spreading by seed or corm, Ixia species tend to hybridise, so sometimes it is difficult to tell whether individuals belong to particular species.
Ixias that have naturalised in Western Australia include I. maculata, which has compact spikes of yellow flowers with brown centres, although white, pink, and red forms, possibly hybrids, have been found.
Another species, I. polystachya, has spindlier growth and smaller pink or mauve flowers, although the population may include white or pale green flowers with blue-green centres that, again, are probably hybrids.
Ixia has invaded woodlands from Perth to Albany, with contaminated areas frequently found alongside old settlements.
Lachenalia or soldier
Four species of Lachenalia have naturalised in urban bushland.
- L. aloides, commonly called soldiers or soldier boys, has tricoloured flowers — usually orange, green, and purple-brown although variations exist.
- L. bulbifera is more robust with red flowers, and it produces many bulbils even from leaf cuttings.
- Flowers of L. mutabilis are pale blue at first, darkening to crimson-brown.
- L. reflexa, which has yellow flowers, is considered a most serious weed, having invaded tuart and banksia woodland and heath in the Perth area.
Sparaxis and harlequin flower
Sparaxis species reproduce by seed, offsets and stem cormels. Many of those found in Western Australia are hybrids, but of the species the commonest is S. bulbifera, which has large cream flowers. It is a serious invader of clay wetlands on the Swan Coastal Plain and in the Avon Valley, often hybridising with purple or yellow S. grandiflora, which occurs in the metropolitan area and wheatbelt.
Harlequin flower (S. pillansii), with tricoloured flowers,usually red and yellow petals and a black centre, is probably the sparaxis most gardeners know best. It has naturalised around old settlements from Perth to Albany.
Bulbil watsonia (Watsonia bulbillifera) is the most invasive of the six Watsonia species naturalised in Western Australia. Despite the common name, technically speaking it is corms, not bulbils, which form on the stem, giving the plant a distinctive silhouette after the orange flowers have died.
Ranging from the size of a rice grain to a large marble, these corms are carried along natural watercourses and in roadside drains. Bulbil watsonia also spreads by seed. It is a serious weed, particularly in damp areas of the south-west and on the south coast.
Another troublesome species is lilac flowered W. marginata, which occurs around old settlements from the Darling Range south to Albany.