Boneseed

Chrysanthemoides monilifera (L.) Norlindh ssp. monilifera

Synonyms - Osteospermum moniliferum. 2 sub-species occur in Australia. Rotundata is mainly on coastal NSW and is more difficult to control than sub-species monilifera that is mainly elsewhere.

Family: Asteraceae.

Names:

Chrysanthemoides is from the Greek words meaning gold (chryos) and flower (anthos) and like (oides). So it is like the gold flowered chrysanthemum.
Monilifera is from the Latin word monile for necklace because the bead-like fruit forms a necklace around the flower head.
Rotundata refers to the rounder or more rotund shape of the leaves of this sub species.
Boneseed refers to the hardness and colour of the seed.
Boneseed is generally used to refer to sub species monilifera.
Bitou Bush is the preferred common name for sub species rotundata.

Other Names:

Bitou bush
Bietou
Brother berry
Higgin's curse
Jungle flower
Salt bush
South African Star Bush.

Summary:

Boneseed is a bushy, woody, erect, perennial shrub to 3 m high with alternate dull, elliptic leaves which are 20-80 mm long, leathery and have margins which are coarsely toothed. The bright yellow daisy flower heads with brownish centres are 10-40 mm in diameter each with 5 or 6 radiating petals. The fruits are globular, 6-8 mm in diameter, with a thin outer fleshy purple-green layer which turns black and flakes off revealing a white bony fruit containing a single egg shaped seed which persists on the bush for several months.
Boneseed is native to South Africa, introduced as a garden plant but now an aggressive weed of roadsides and disturbed woodland. It flowers mostly in late winter and spring.
Chrysanthemoides monilifera subsp. rotundata (Bitou Bush) is very similar but usually only up to 2 m high and with more rounded spoon shaped leaves. The flower heads differ in having 11-13 radiating petals. The fruits are slightly smaller, egg shaped and ribbed. Bitou bush flowers all year round and can be a serious weed of coastal areas.

Description:

Cotyledons:

Two. Club shaped.

First leaves:

Oval. Edges toothed.

Leaves:

Dull green. Alternate, 15-80 mm long. Paddle shaped. Tip pointed. Hairless or with cobweb hairs, especially on young leaves or near the tip or with terminal tufts of cottony down.
Petiole - Short and narrow.
Blade - Egg shaped to lance shaped to oval. 15-80 mm long x 7-25 mm wide. Tapering at the base. Edges irregularly, coarsely toothed. Tip pointed. Hairless apart from cottony down on young leaves.

Stems:

Erect, woody, many branched. Often purplish near the ends of stems. Hairless or with cobweb hairs. Forms a shrub about 1000-2000 mm wide and 500 to 3000 mm tall and occasionally to 6000 mm tall.
It has a many branched stem that arises as a single stem from the root crown.

Flower head:

Corymb at the ends of stems. Bright yellow daisy type flowers. Bell shaped. 20-30 mm diameter on short stalks, densely clustered at the ends of branches.

Flowers:

Bracts - 2 or 3 rows of thin, egg shaped bracts under the head.
Florets - 5-8 fertile ray florets, female with yellow, 3 toothed, egg shaped to oval 'petals' in a single ring. Central disc florets, tubular, brown, 5 lobed, male or bisexual and sterile with a funnel shaped, hairy tube.
Ovary -
'Petals' - 5-8, bright yellow, 3 toothed, in a single ring. 10-15 mm long.
Stamens -
Anthers - Shortly tailed with an egg shaped appendage near the tip.

Fruit:

Achene. Globular to egg shaped. 6-8 mm diameter. Smooth. Purple green, fleshy skin initially that turns black then flakes off to expose the bony, hard, white inner coat when dry. One seed in each fruit.

Seeds:

No pappus. Globular to egg shaped, hard and bone coloured.

Roots:

Shallow. No distinct taproot. Ssp. rotundata has a larger and more aggressive root system than ssp. monilifera.

Key Characters:

Biology:

Life cycle:

Perennial shrub.
Seed germinates mainly in autumn and grows rapidly. It will grow throughout the year as an evergreen whenever moisture is available. Maximum growth is usually in spring and early summer. Some may flower in their first year but most take 2-3 seasons. Different sub-species flower at varying times but usually with a peak in winter and spring. Seeds are produced in late spring to early summer. Seeds are often retained on the bush for some time and shed mainly in summer. Just over half of the seed produced is viable. This seed germinates when the hard outer coat splits. Seed may survive in the soil for over 10 years. The shrub survives for 10-20 years.

Physiology:

Tolerates saline conditions.
Does not tolerate water logging or prolonged drought. Young growth is frost sensitive but the plant usually recovers.
Fire kills mature plants but also encourages germination of seed.
More responsive to phosphorous and other nutrients than native vegetation.

Reproduction:

By seed.
Self pollinating and cross pollinating with a range of insect vectors.

Flowering times:

July to October in SA.
Spring to summer in NSW.
March to October in Perth.
Odd flowers in July with a flush in September/October and mature fruit from November to early January in Victoria.

Seed Biology and Germination:

It produces up to 50,000 seeds per plant and has a large seed bank in the soil (800-2500 seeds/m2 for ssp. monilifera and to 9500 seeds/m2 for ssp. rotundata). Fire stimulates germination and recruitment.
Some ssp. monilifera seed lasts at least 10 years. 13% was viable after 3 years. Some seed of ssp. rotundata lasts in the soil for around 4 years.
Viability of seed increases with depth of burial.
Germination is increased by fire, soil disturbance, weathering and passage of seed through birds and animals.
Fire splits the seed sutures allowing absorption of water and germination.

Vegetative Propagules:

Ssp. rotundata roots where the branches make contact with the soil.
Coppices when cut.

Hybrids:

Several sub species occur.
Boneseed will hybridise with Bitou Bush giving plants of intermediate characteristics.

Allelopathy:

Produces toxins from the leaf litter and fruit leachate that reduce the germination and or vigour of neighbouring plants.

Population Dynamics and Dispersal:

Rapidly colonises denuded areas and sand dunes.
Boneseed is spread by seed dispersal by birds, rabbits, foxes, stock, ants, gravel for roads, garden refuse, in running water and rolling down slopes.
Its main spread has been by intentional planting or escapes from rubbish dumps.
It often establishes in areas of road making, clearing or burning. It regenerates from seed quickly after fire.
Establishes quickly form seed.

Origin and History:

Native to South Africa (Western Cape Province).
Introduced to Sydney, Melbourne and Adelaide as an ornamental in the 1850's and was first recorded in the wild in 1852 in Sydney and 1892 in Adelaide. By 1910 it was considered to be naturalised.
Sub species rotundata was introduced in ships ballast to the Hunter River around 1908.
Between 1946 and 1968 it was planted to stabilise sandy areas.

Distribution:

Sub species monilifera is in NSW, SA, TAS, VIC, WA.
There are many small and isolated infestations and major infestations at You Yang Range and Mornington Peninsula in Victoria and Mt Lofty ranges in South Australia.
Naturalised in France, Sicily and St Helena.
Sub species rotundata is in NSW, QLD, VIC, WA.

Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Sub-tropical and sub-humid.
Sub species rotundata prefers summer rainfall areas and ssp. monilifera prefers winter rainfall areas.

Soil:

Prefers light soils. Sand dunes. Loams.

Plant Associations:

Wide range from mallee scrub to wet and dry sclerophyll forest.
Scrubland, coastal woodlands, open forest.

Significance:

Listed as a "Weed of national significance" in Australia and a "National surveillance pest plant" in New Zealand.

Beneficial:

Ornamental plant.
Prior to 1968 it was used for rehabilitating sandy areas and mines.
Stabilises soil.
Provides shelter.
Fruits are edible and can be used to make jam.

Detrimental:

An aggressive weed especially in coastal areas where it colonises dunes. It often eliminates all other native species. Weed of roadsides and disturbed areas. It is one of the few weeds that will invade undisturbed bush. It regenerates very quickly after fire.
It is an environmental weed rather than an agricultural weed.
It has a more efficient leaf arrangement and more vigorous root system than native species giving it a competitive advantage. It is listed as a threat to Brittle greenhood orchid (Pterostylis truncata) and Coast Manna Gum (Eucalyptus viminalis).

Toxicity:

Not recorded as toxic.

Legislation:

Noxious weed of NSW, QLD, SA, TAS, VIC, WA and LHI.
In WA all infestations are eradicated.
Banned from sale in New Zealand.

Management and Control:

Ssp. rotundata is more aggressive and more difficult to control than ssp. monilifera.
Boneseed occupies on a small area of its potential range so prevention of spread from existing sites and vigilance at rubbish tips is very important.
Identify sources of potential infestation and control plants in these areas.
Burn contaminated refuse. Restrict movement of seed by addressing soil movement, animal and vehicle control and public education.
Mulching has not been very effective overall unless it is associated with transplanting of native species because it tends to retard the naturally regenerating species as much or more than the Boneseed.

Thresholds:

Eradication strategies:

Small infestations can be mechanically removed and burnt quite easily because it has a shallow root system.
Cultivation and trampling provide control in agricultural situations.
It is controlled by grazing and is rarely found in pasture.
Cultivation and mechanical removal are effective but often not desirable on the fragile soils infested. Mowing and slashing is ineffective because of prolific regrowth from the cut stumps. Removal of bushes usually results in a mass of seedlings germinating. Fire kills plants and some surface seed and encourages mass seed germination when done in late summer. These seedlings may then be controlled within 16 months of germination (i.e. before the seedlings flower). Herbicides are preferred because they cause less soil disturbance which may encourage Boneseed and other weeds to establish. If manually removing seedlings then tamp the ground with your foot after the seedling has been pulled up and recover the disturbed area with litter. Hand pulled plants can be left on site providing the roots are not in contact with the soil and they are not carrying seed. Seed collected from control programs should be burnt.
The preferred burning strategy is to cut old woody plants and let them dry for at least a month the use a medium intensity fire from September to April when fine litter is dry.
Gas fired burners have been used in low litter or moist situations.
Bromoxynil provides effective control of seedlings. Several other herbicides such as glyphosate, picloram, amitrole, metsulfuron also provide good control as overall sprays. Glyphosate and 2,4-D are also used for cut stump applications. Aerial applications of glyphosate have also been used in native bush situations with little damage to the native species.
Control may need to be integrated with a revegetation program to prevent other introduced weeds invading areas where boneseed has been controlled. However, In many cases where infestations have not been dense or long lived then natural revegetation will be sufficient. Follow up programs or inspections every second year (and after every fire) for 10 years are desirable to prevent re-establishment of the infestation from dormant seed.

Herbicide resistance:

Biological Control:

A biological control program has released a tip attacking moth in 1989, a leaf eating beetle in 1990 a seed fly and 3 other insects up to 2000. The Bitou tip moth is the only one that has established. Other agents including a rust fungus are under evaluation.
High rabbit numbers are thought to reduce its spread because they eat the seedlings.
Sheep, cattle and goats control it on agricultural land.

Related plants:

C. monilifera ssp. rotundata is very similar but is usually smaller, up to 2000 mm tall unless supported and sprawling rather than erect. There are up to 11-13 ray florets in the head rather than 5-6, the fruit is smaller and egg shaped rather than globular being 5-7 mm long and 3-4 mm wide and longitudinally ribbed rather than smooth and the inner phyllaries are narrower. The seeds are smaller, darker, more egg shaped and ribbed The leaves are rounder, the leaf margins are less distinctly toothed. The prostrate stems produce roots where they contact the soil. It flowers all year with a peak in April to June rather than the more contracted flowering of ssp. monilifera in winter and spring.
There are no closely related native plants.

Plants of similar appearance:

Osteospermum species are similar but don't have fleshy fruit.

References:

Adair, Robin and Ainsworth, Nigel (2000) Boneseed. CRC for Weed Management Systems Adelaide.

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P93. Photo.

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P890. Diagram.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P682. Photo.

Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne). P75. Photo.

Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #244.1, 244.2.

Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P668.

Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P273-277. Photos.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.