Hieracium robinsonii (Zahn) Fern.
Habitat: Crevices of ledges and rocky shores.
Range: Newfoundland and Quebec south to Maine and New Hampshire.
Aids to Identification: Identification of hawkweeds often relies on microscopic features, making identification in some cases very difficult. Robinson’s hawkweed differs greatly from the common orange hawkweed (Hieracium aurantiacum) that is found in lawns and fields, by having basal leaves with long petioles (nearly sessile in H. aurantiacum) and 4-10 nearly glabrous leaves along the stem that decrease in size up the stem. The image on the above pdf shows H. lachenalii, an introduced hawkweed that H. robinsonii could be easily confused with. The two can be separated by the presence of glands on the involucre bracts and pedicels of H. lachenalii; H. robinsonii may have minute glands as well but not as many as H. lachenalii. H. robinsonii has long villous hairs around the inflorescence (H. lachenalii has shorter and fewer villi). The habitat of H. robinsonii can also help separate the two.
Ecological characteristics: Little is known ecologically about this plant in Maine, has not been seen recently.
Phenology: Flowering late June through September.
Synonyms: Hieracium ungavense Lepage.
Known Distribution in Maine: This rare plant has been documented from a total of 7 towns in the following counties: Aroostook, Piscataquis, Somerset.
Reason(s) for rarity: Approaching southern edge of range, scarce throughout range.
Conservation considerations: Unknown, has not been documented recently.