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    Interested in what's new with Hawkweed biocontrol research?  Download the CABI Annual Report on Hieracium for 2010 here.

    Montana Hawkweed Identification Bulletin now available.  To order more copies, contact Montana State University Extension Publications by clicking here.

     

  • resources

    Check out our resources page with many guides, fact sheets, and regional maps to help you identify the hawkweed complex. 

       

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    Established in 1948 as the Europe Station of the Commonwealth Institute of Biocontrol, CABI Europe-Switzerland has traditionally worked on the classical biological control of invasive insect pests and weeds of Eurasian origin, on behalf of the temperate areas of the world, particularly North America, Australia, and New Zealand.

     

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    hawkweed biocontrol consortium

    invasive hawkweeds

    Orange hawkweed flower.  Photo by Gitta Grosskopf-Lachat.
    Orange Hawkweed.  Photo by Gitta Grosskopf-Lachat.

    Hawkweeds are fibrous-rooted, perennial herbs growing from a stout rhizome.  Plants reproduce by seeds and vegetatively by stolons, rhizomes, and adventitious root buds. 
    Stolons are present on some invasive hawkweed species.
    Stolons are present on some invasive hawkweed species.

    The small, dandelion-like heads are borne singly at the top of long, hairy to hairless stems. The inflorescences are flat-topped-to-rounded and compact.  One invasive hawkweed specie has an orange flower while all other species has yellow flowers.  Invasive hawkweed rosettes have long near-linear leaves with few and less prominent hairs.  Seed production is primarily asexual through apomixis (the production of seeds without pollen). 

    Kingdevil hawkweed, another invasive hawkweed in North America.
    Kingdevil hawkweed, another invasive hawkweed in North America.

    Hawkweeds are distinguished largely on a few key morphological characters, including leaf, stem and phyllary (involucral bract) pubescence.  Hairs, both type and abundance, are important characters used to distinguish hawkweed species.  These types of hairs are common:  long simple hairs; dark, glandular hairs; and small, star-shaped (stellate) hairs.  Invasive hawkweeds also tend to have few stem leaves that are greatly reduced in size and found mostly on the lower half of the stem. 

    hybridization

    All invasive hawkweeds in North America are polyploid (n=9) and typically asexual, compared to the entirely diploid and sexual native species.  Hybridization between invasive and native hawkweeds most likely is not possible.  However, hybridization between invasive polyploid hawkweeds could be possible but to date is not scientifically documented.