Montbretia

NOXIOUS WEED:  Class 4

Crocosmia x crocosmiiflora

family: IRIDACEAE

Description

• Vigorous, perennial hybrid bulbous plant from South Africa, which dies down in autumn after producing annual leaves and flowers.
• Leaves are bright green, spear-shaped, and appear in spring.
• Long spikes of small orange to red tubular flowers appear in summer.
• Each plant bears a string of flattened corms under the ground, up to 14 or more, each capable of producing another plant. Also produces rhizomes, and in some situations a mass of fine fibrous roots is also formed.
• Montbretia can tolerate a wide range of environmental conditions - it grows in any soil, wet or dry, poor or rich, in sun or shade. It can be seen on roadsides, wasteland and the disturbed edges of bushland. However, it thrives along creeklines and watercourses where it spreads with great vigour, fed by nutrients in the stormwater, and competes fiercely with all other plants, including other weeds.

Dispersal

Spreads vigorously by corm production, and perhaps by seed. Rhizomes produce new plants. Corms wash down watercourses to form new infestations. The plant is also dispersed by the movement of soil containing corms, and is frequently dumped on bushland edges.

Impact on Bushland

Montbretia reproduces vegetatively with great vigour. Each corm is a potential new plant, and will shoot when broken free from the parent plant. Corms live and produce plants for two years or more, and new corms are formed annually. Long rhizomes are also produced, each of which grows into a new plant.

Montbretia displaces native creekline plants. It moves rapidly down watercourses into sensitive bushland. The mass of corms in the soil contributes to the breakdown of creek banks, erosion and siltation. Responsible for serious habitat loss.

Distribution

Throughout the Blue Mountains.

Alternative Planting

Native Plants
Local native Water-ferns (Blechnum species)
Saw-sedges (Gahnia species)
other local sedges such as Juncus, Isolepis, Schoenus species

Exotic replacements
Jacobean Lily (Sprekelia formosissima)

Control

Dig deeply to remove all corms. Pulling this plant out will lead to corms breaking off to form new plants, increasing the problem.
Wipe leaves.
Spray in summer to autumn, using 13ml glyphosate per litre of water.

Montbretia is a Class 4 Noxious Weed.

Characteristics
Class 4 noxious weeds are plants that pose a threat to primary production, the environment or human health, are widely distributed in an area to which the order applies and are likely to spread in the area or to another area.

Control objective
Minimise the negative impact of those plants on the economy, community or environment of NSW.

Control action
The growth and spread of the plant must be controlled according to the measures specified in a management plan published by the local control authority, and the plant may not be sold, propagated or knowingly distributed.

— NSW Noxious Weeds Act of 1993

More Information

Weed of the Month article about Montbretia.