Orange hawkweed (Hieracium aurantiacum)

Orange hawkweed

(Hieracium aurantiacum)

Description

  • Orange hawkweed is a perennial plant native to the alpine regions of central and southern Europe
  • Bright orange, orange-red, or yellow flowers with several flower heads in clusters
  • Stems are usually single, unbranched and leafless; leaves are found at the base of stem in basal rosette formation (native hawkweeds will have true leaves all the way up their stems)
  • Stems are covered in black hairs
  • 0.3 – 1.2m tall

Consequences of invasion

  • Invasive hawkeed species can replace native vegetation in open, undisturbed natural areas
  • Reduce forage and threaten biodiversity
  • Outcompetes forage plants in hay fields and pastures

Integrated Pest Management Options

  • For small infestations, dig out rosettes and their shallow roots and dispose in clear plastic bags for free
  • Do not spread any vegetative parts of the plant as regrowth can occur
  • Mowing removes flower stems and may prevent seed set, it should be used with caution as it encourages vegetative spread
  • Large infestations can be treated with high nitrogen fertilizer , try 34-0-0 granular nitrogen which is available from Nelson Farmer Supply.
    • You can broadcast the fertilizer (3kg/200m2) or use spot treatment (approx 5-12g of granular fertilizer per basal rosette).
    • Treat AFTER a period of moisture rain or dew (water activated) but BEFORE a sunny period (so fertilizer doesn’t wash away). Also, treat BEFORE flowers set, otherwise you will need to remove seed heads
    • Mortality and decrease in density will be visible within two weeks, however follow-up treatments are needed to get distribution down. Hard packed and sloped surfaces take longer to treat.
    • Grasses will be boosted, as will other tap roots (knapweed, thistle), and over-fertilization can kill most things, including trees so be mindful of surrounding vegetation.
  • Minimize soil disturbance and promptly revegetate disturbed areas
  • Become Plantwise and learn about Grow Me Instead

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