Creeping knapweed (Acroptilon repens) is a weed of horticultural and cereal crops, roadsides and wasteland. It can reduce cereal crop yields by 75%.
- perennial, erect thistle-like herb to 1m, dense soft greyish hair on leaves
- greyish green stems are erect, thin, stiff, branched, 45-90cm
- leaves in a basal rosette and lobed, 15cm x 5cm, withering in mature plants
- solitary flower heads are lilac or pink, turning straw coloured at maturity 1-1.5cm long
- oval seeds, 3-4 mm long, cream or mottled striped lengthwise with easily detachable stiff barbed hairs at one end
- deep and extensive root system can extend more than 7 metres below the soil surface.
Why is it a problem?
- competitive weed that can severely reduce crop yields
- taints grain and flour with a bitter, unpleasant flavour, may inhibit the growth of surrounding plants
- invades disturbed and cropping areas
- removes vital moisture and nutrients from the soil in summer
- poisonous, but generally avoided by grazing animals due to the bitter taste.
- Eastern Eyre Peninsula
- Lower and Upper Yorke Peninsula
- Mid North Agricultural district
- Murray Mallee and Riverland regions.
- one plant can produce 1,200 seeds annually
- inhibits surrounding plant growth and spreads outward into previously un-infested areas
- extensive root system can extend more than 7 metres below the soil
- horizontal roots have buds which can give rise to new aerial growth.
How it spreads
- root fragments broken off during cultivation is the primary method of spread
- seed dispersed in the manure of livestock.