Calomba daisy (Oncosiphon suffruticosum) is an annual, aromatic, unpalatable pest plant that competes with more valuable pastures for water, light and nutrients.
- erect strongly chamomile-scented annual herb to 60cm high
- leaves are grey-green, 2-4cm long, of a feather like appearance, first leaves form a small rosette
- flowers are tiny and mustard-yellow, at the end of stems in broad flat groups of ball-shaped heads
- each flower forms a seed 2mm long, resembling fine chaff.
Why is it a problem?
- unpalatable to stock, but if eaten by stock will taint meat and milk products
- reduces the growth of pasture species via chemicals it releases into the soil
- dense stands can also reduce the yield of cereal crops.
- Northern Adelaide Plains
- Upper Yorke Peninsula
- Isolated infestations in the Mallee region.
- plants remain rosettes over winter, flower stems develop in August
- seeds germinate in autumn
- plants die in early summer leaving dry woody stems carrying the seeds
- seedlings are tiny and require gaps in pasture or bare ground to establish.
How it spreads
- found in disturbed soils or cultivated fields, degraded pastures and roadsides
- seeds are spread when the flower head is broken off and moved by wind, or by animals and vehicles
- seeds can also be carried as a contaminant in fodder and produce.