Crofton Weed

NOXIOUS WEED:  Class 4

Ageratina adenophora

family: ASTERACEAE (daisy family)

Description

  • An erect, bushy, leafy, many-stemmed herbaceous perennial to 2m, from Central America. Forms dense stands, prefers moist, nutrient-rich soil, is common in disturbed areas. Also known as Eupatorium adenophorum, and Mexican Devil. Poisonous to horses.
  • Leaves are opposite, soft, thin, shaped like a triangle or rhombus, with a toothed edge and conspicuous veins. They are dark green on the upper surface, lighter underneath, and may be slightly hairy; 4-12cm long, 3-9cm wide. Layers at leaf nodes.
  • Flowers profusely in spring and summer, producing dense clusters of white sticky hairy flowers, 5-8mm in diameter, at the ends of the branchlets.
  • Seed production is enormous - 10,000 to 100,000 per year when mature. The seeds are very small, light, brown to black, with a 4mm 'parachute' of white hairs, mid to late spring. Germination rates are high.
  • Has a tap root, and a shallow but extensive fibrous root system.
  • All parts of the plant have a strong aromatic smell when bruised, which may cause allergic reactions.

Dispersal

Seed is dispersed by wind and water over long distances, and is also moved by vehicles and machinery, and in clothing, soil and stockfeed. Also spread by garden dumping.

Impact on Bushland

A highly invasive plant, tolerant of a wide range of conditions, common on roadsides and bushland edges, along watercourses, creeks, and in wetlands. Capable of infesting intact bushland and displacing native plants; an increasing problem.

Distribution

Throughout the Blue Mountains, including the Mounts, but more common from Bullaburra to Lapstone.

Alternative Planting

Native Plants
Correas (eg Correa reflexa)
Daisy Bushes (Olearia elliptica, Olearia myrsinoides)
Waxflower (Phylotheca myoporiodes, formerly Eriostemon)

Exotic alternatives
Mock Orange (Philodelphus species)
May Bush (Spiraea x vanhouttei)

Control

Hand remove, taking all roots; bag flower and seed heads; do not leave stems on ground. Will reshoot if damaged. Large infestations can be sprayed in spring and summer. Get advice from Council or DIPNR if growing along watercourses - you may need a permit. Survives 'cool' burns, otherwise destroyed by fire. Be prepared for follow up treatment.


Crofton Weed can form dense stands in intact busland, excluding native plants.
photo: © Barbara Harley

Crofton Weed 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

Picture of Crofton Weed leaves

Leaves of Crofton Weed are soft and thin, and shaped like a triangle or a rhombus.
photo: © Barbara Harley

Picture of Crofton Weed flowers

Spring and summer flowers are dense, white, hairy and sticky, producing numerous tiny seeds.
photo: © Barbara Harley

Picture of Crofton Weed habitat

Crofton Weed prefers sheltered, moist, nutrient-rich conditions (seen here on the edge of rainforest), but ...
photo: © Barbara Harley

Picture of Crofton Weed habit

... this plant is tough enough to grow almost anywhere.
photo: © Barbara Harley