Field Scabious
(Blue buttons, knautia)
What does it look like?
Field scabious (Knautia arvensis (L.) Duby) is a simple perennial that reproduces and spreads by seed. It has pale purple to blue flowers in dense heads composed of numerous, tube-shaped florets. Stems can grow up to 1.3 metres tall and are sparsely branched. Very often the entire plant (including the flower buds) is covered in short, stiff hairs. The leaves are opposite and deeply divided into 5-15 narrow segments.
Its weedy nature...
Field scabious is a non-native plant of European origin. It is found primarily in pastures, waste places and roadsides. It is a very effective competitor, and is difficult to remove once established. It can quickly take over pastures where competition by desired species is reduced, such as in an overgrazed pasture situation. Although this plant is not poisonous to livestock it is very unpalatable when mature with little nutritional value. Cattle will eat young plants before they bolt.
Its control
Field scabious cannot survive repeated cultivation, so it is not a problem in annual crops. In very severe infestations, intense cultivation with a disc will destroy roots for that season. Planting to an annual crop is then recommended to effectively out compete remaining plants.
Mowing to prevent the spread of seed before flowers form is the best method of cultural control. Field scabious flowers briefly in late June to early July so low mowing at bolting (when the plant begins to rapidly get taller) is suggested. Infested areas should be monitored for regrowth throughout the summer and mowed again if necessary.
If mowing is done after flowers have formed, mowed plants should be gathered and disposed of by burning or placed in a sanitary landfill, as field scabious seeds are viable almost as soon as flowers form. All equipment used should be thoroughly cleaned to prevent seed transfer to non-infested sites.
For small infestations, hand pulling is very easy and highly effective. A combination of mowing and cultivation can also be used.
Split applications of some herbicides during the spring and again in the fall of the same year have given very positive results for heavier infestations.
At the present time there is no registered herbicide for the control of field scabious, but you are encouraged to call Transportation and Agriculture Services 417-7132, to discuss options best suited for your situation.
A note on fertilizer use...NPK
Dense stands of grass compete well with field scabious, however fertilizer alone can enhance the growth of this weed. In areas that are infested, always combine a pasture fertilization program with chemical or cultural weed control.
Further Information
Transportation and Agriculture Services
780-417-7100
Photographic credits to Alberta Agriculture, Food and Rural Development, the British Columbia, Ministry of Agriculture, Food and Fisheries, Field Guide to Noxious and Other Selected Weeds of British Columbia and Strathcona County, Transportation and Agriculture Services.
Photographic credits to Alberta Agriculture, Food and Rural Development, the British Columbia, Ministry of Agriculture, Food and Fisheries, Field Guide to Noxious and Other Selected Weeds of British Columbia and Strathcona County, Environmental Operations.
Last updated: Wednesday, March 31, 2010
Page ID: 3501