Ageratum houstonianum, commonly called floss flower, is a frost-tender annual of the aster family that provides continuous bloom for beds, gardens or. A. houstonianum is an annual herb native to Mexico and Central America. It was brought to Europe shortly after its discovery, where its use as. There are many cultivars available of this fast-growing annual. They are best used as bedding, edging, or container plants. Panicles of blue, pink, purple.

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Click on images to enlarge. Blue billygoat weed Ageratum houstonianum has been widely cultivated as a garden ornamental, and in cultivation it is often known as “floss flower”.

There are many different cultivars, which vary in size and flower colour i.

This species is widely naturalised in the coastal districts of eastern Australia i. Also widely naturalised in the tropical regions of the world, including south-eastern USA i.

Hawaii, Fiji and French Polynesia.

Ageratum houstonianum (Blue billygoatweed)

A weed of gardens, roadsides, disturbed sites, waste areas, pastures, crops, wetlands and waterways in the tropical, sub-tropical and warmer temperate regions of Australia.

The leaves are mostly oppositely arranged, but can be alternately arranged on the upper parts of the stems. They are borne on stalks i.

These leaves cm long and 1. agdratum

Floss Flower: How To Care For Ageratum Houstonianum

Both surfaces of the leaves and the leaf stalks have a scattered covering of hairs i. Each flower-head mm across has numerous tiny tubular flowers i. The bracts at the base of the flower-head mm long are elongated in houstoniianum i.

Flowering occurs throughout most of the year. These scales mm long are whitish in colour and resemble short bristles or hairs.

Ageratum houstonianum

This species reproduces by seed. The tiny, light, seeds are often dispersed by wind and water. They readily become attached to animals, clothing and vehicles and may also be spread in contaminated agricultural produce. Blue billygoat weed Ageratum houstonianum is regarded as an environmental weed in Queensland and New South Wales. This garden escape frequently invades bushland and other natural environments resulting in substantial changes in native plant communities.


Ageratum Houstonianum. The Blue Floss Flower. The Perfect Blue Annual.

It displaces indigenous plants, and possibly also native animals, and is particularly invasive along waterways and in riparian vegetation. In Queensland, blue billygoat weed Ageratum houstonianum is currently of most concern in the south-eastern parts of the state, where it is ranked among the top environmental weed species.

For example, blue billygoat weed Ageratum houstonianum is one of only a few introduced species that have colonised undisturbed or relatively intact open forest vegetation within Brisbane Forest Park. In New South Wales, blue billygoat weed Ageratum houstonianum is primarily of concern in the central and northern coastal regions.

It appears on the “Bushland Friendly Nursery Scheme” list of environmental weeds for north-eastern New South Wales and on several local weed lists in this region i.

It also appears on local and regional environmental weed lists further south i.

Blue billygoat weed Ageratum houstonianum is also considered to be among the most invasive species in southern Africa, and is thought to pose a threat to the biodiversity of this region. It is one of several closely-related species that are invading savannas, grasslands, forest margins, riverbanks and wetlands in South Africa and neighbouring countries i.

Swaziland, Mozambique and Zimbabwe. It often forms dense stands that exclude other species and there is evidence to suggest that it has allelopathic properties that inhibit the growth and germination of other plants.

This species is a very common weed of sugar cane crops in Queensland, and is also a weed other cropping systems in the coastal areas of southern and central Queensland. This species is not declared or considered noxious by any state or territory government in Australia. Blue billygoat weed Ageratum houstonianum is often confused with another very similar species, billygoat weed Ageratum conyzoides. These species can be distinguished by the following differences:.


Another environmental weed, praxelis Praxelis clematideaand a native plant, vernonia Cyanthillium cinereumare also very similar to blue billygoat weed Ageratum houstonianum. Vernonia Wgeratum cinereum leaves have finely-toothed i. Check our website at www. The control hoistonianum referred to in this fact sheet should be used in accordance with the restrictions federal and state legislation, and local government laws directly or indirectly related to each control method. These restrictions may prevent the use of one or more of the methods referred to, depending on individual circumstances.

While every houstoniaum is taken to ensure the accuracy of this information, DEEDI does not invite reliance upon it, nor accept responsibility for any loss or damage caused by actions based on it.

Sheldon Navie large infestation in a pasture Photo: Sheldon Navie habit Photo: Sheldon Navie paired lower leaves with slightly heart-shaped bases Photo: Sheldon Navie close-up of hairy stems, alternately arranged upper leaves, and young flower-heads with hairy bracts Photo: Sheldon Navie branched clusters of flower-heads at the sgeratum of the stems Photo: Sheldon Navie close-up of flower-heads showing their long floral projections Photo: Sheldon Navie plants with white flower-heads are occasionally seen Photo: Sheldon Navie close-up showing the numerous tiny flowers in each flower-head Photo: Sheldon Navie young plant and seedlings Photo: Sheldon Navie old flower-heads and ‘seeds’ Photo: