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
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.
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.
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.