Hieracium sect. Umbellata
- Latin synonym: Hieracium Hieracioides group
- Name also: Narrowleaf Hawkweed, Northern Hawkweed, Canadian Hawkweed, Canada Hawkweed
- Family: Daisy Family – Compositae, subfamily Cichorioideae (formerly Chicory Family – Cichoriaceae)
- Growing form: Perennial herb. Runnerless.
- Height: 5–75 cm (2–30 in.). Stem ascending–erect, delicate–sturdy, grooved, glabrous–sparsely hairy, upper part also stellate-haired.
- Flower: Single flower-like capitula under 2 cm (0.8 in.) broad, surrounded by involucral bracts. Capitulum flowers yellow, tongue-like, tip 5-toothed. Stamens 5. Gynoecium composed of 2 fused carpels. Involucral bracts in many rows, overlapping, different lengths, with tapering and spreading tips, usually almost glabrous, without glands, usually virtually black, occasionally dark green or brownish. Capitula an umbellate group (sometimes with 1 capitulum in barren places).
- Leaves: Alternate, short-stalked–stalkless. Lacking basal rosette, stem leaves 10–30. Blade lanceolate–linear, with tapering tip and base, quite hard, top dark green, almost glabrous–short-haired, underside with bristle hairs, margin entire or sparsely toothed, recurved.
- Fruit: Uniformly thick–widening towards tip, ca.10-ridged, brownish-black, 3–4.5 mm (0.12–0.18 in.) long achene, tip with ring-like border and slightly brownish, unbranched hairs.
- Habitat: Dry, bare sea and lake shores and river banks, road and rail embankments, rocky outcrops, openings in forest heaths, forest margins, ridged slope, gravel pits, wasteland, field banks.
- Flowering time: July–September.
Leafy hawkweeds are an exception within genus Hieracium in that they are easily identifiable. They have dense capitula which are tightly gathered in a virtually umbellate group. They are also characterized by their abundant, narrow leaves which have recurved edges and entire or sparsely-toothed margins. In many other respects leafy hawkweed mutates easily: with regards to its size, growing form, sturdiness, hairiness, the number of capitula and the colour of its involucre.
The diversity of hawkweeds is mainly due to the fact that they are apomictic: their seed subject doesn’t have to be fertilised because they receive their DNA directly from the mother plant. This means that all new plants are direct copies of their mother and even the smallest hereditary mutations constitute an independent lineage, known as a micro-species. Unlike other members of its genus, however, leafy hawkweed also reproduces sexually: some micro-species hold on to their tiny, apomictically-produced differences, while others reproduce sexually and also cross-breed with closely-related micro-species to produce new types. Leafy hawkweeds are therefore not much less diverse than other genus Hieracium plants. Other common closely-related species groups in Finland are common hawkweeds (H. Vulgata) and wall hawkweeds (H. Sylvatica). Its close relatives in genus Pilosella have runners and scapes.
Leafy hawkweeds are common across Finland in dry and quite dry places. Often it is very conspicuous as it grows on barren heaths, sloping meadows, roadsides, railway embankments and storage areas. The lovely yellows that embroider the roadsides at the end of summer are due in large part to leafy hawkweed and it is a good nectar plant, offering nutrition to insects after other plants have withered. Leafy hawkweed thrives in sandy ground and on shores it is an important plant for keeping the sand in place.