Hawkweeds (Hieracium)

Group I & II. plants with a well developed cluster of basal leaves at flower time, these generally as large as or larger than any of the upper ones; infl corymbiform (or the heads solitary), not elongate

Group I. plants stoloniferous; rhizome generally elongate

Group II. plants not stoloniferous; rhizome generally short & praemorse

Group III. plants either without a well developed cluster of basal leaves at flower time, or with an elongate, cylindric infl, or both

Group I.

..... lvs hairy hairy only on one side not hairy
3) heads solitary (rarely 2 or 3) Mouseear h.w. (1.pilosella) heads us solitary (sometimes 2) weed in pastures & fields; Eurp, now widespread ..... .....
3) head 2-many (rarely solitary on some invivs of #2) ..... ..... .....
4) heads mostly 2-6, long-pedunculate; fls yellow ..... ..... large mouseear h.w. (2.glagellare stem stout; field & along roadsides; Elurp, sparingly intro into QE to NY
4) heads 5-50, short-pedunculate in a compact, corymbiform infl ..... ..... .....
5) fls yellow ..... ..... .....
6) herbage not glaucous; lvs glabrous or nearly so above; 1/2-3/4" wide fl head ..... .pale h.w. (3.floribundum) upper lf surface smooth; meadows; roadsides & fields; Eurp, NB & ME to NY .....
6) herbage not glaucous; lvs hairy on both sides 1/2-3/4" wide field h.w. (4.caespitosum) stem & lvs very hairy; fields, pastures & along roadsides, occ in dry woods; Eurp, widespread; se Can to n GA ..... .....
5) fls red-orange, becoming deeper red in drying; 3/4-1" wide fl heads orange h.w. (5.aurantiacum) fields, roadsices & meadows; Eurp, widespread; se Can to NC ..... .....

Group II.

..... BE .....
..... purple-veined hairy
7)achenes 1.5-2.0mm ..... .....
8)herbage glaucous, sparsely hairy to subglabrous glaucous king-devil h.w. (6.piloselloides) weed of fields, meadows, pastures & roadsides; Eurp, well estab nearly throughout .....
8)herbage not glaucous; lvs hairy on both sides ..... field h.w. (4.caepitosum) stem & lvs very hairy; weed in fields, pastures & along roadsides, occ in dry woods; Eurp, now widespread, se Can to n GA
7) achenes 2.2-4mm ..... .....
9) fls 40-80 per head; at least some of the lvs gen sharply toothed near the base; intro weed, except #9 ..... .....
10) basal lvs broadly rounded or truncate to cordate at base ..... wall h.w. (7.murorum) along roadsides & in other waste places; Eurp, sparing intro; NS to NY & NJ
10) basal lvs (as well as the cauline) tapering to the petiole ..... .....
11) spreading hairs of the peduncle mostly gland-tipped; basal lvs 1.5-5cm wide; plants 1.5-10dm; widespread; 1.5" wide heads ..... common h.w. (8.lachenalii) leaves often mottled w/ purple
11) spreading hairs of the peduncle mostly gland-tipped; basal lvs 2cm wide or less; plants 1-3.5dm; n NH & northward ..... northeastern h.w. (9.robinsonii) X
9) fls 15-40 per head; lvs entire or merely callous-denticulate ..... .....
12) basal lvs evid purple-veined in life rattlesnake h.w. (14.venosum) mostly in dry, open woods; NY to VA & n GA .....

Group III.

..... AE hairy AT
13)achenes distinctly narrowed toward the summit ..... .....
hairs of the lower part of the stem seldom approaching 1cm; fls mostly 20-40 per head hairy h.w. (16.gronovii) .....
13) achenes truncate, only very obscurely if at all narrowed upwards ..... .....
15) fls mostly 8-30 per head;yellow fls; 1/2"wide ..... panicled h.w. (15.paniculatum) woods; NS to VA & in mts to GA
15) fls mostly 40-110 per head ..... .....
16) peduncles densey & conspicuolusly long-stipiate-glandular; 1/2-1" wide rough h.w. (18.scabrum) open ground & dry woods, esp in sandy soil; NS to VA & in mts to n GA .....
16) peduncles merely stellate    
17) lower part of the stem & lower lf-surfaces provided with long, firmly bulbous-based hairs, not at all stellate; intr. weed (10.sabaudum) Eurp, estab as a weed; MA to PA .....
17) plant without long, bulbous-based hairs; lvs us but not always finely stellate; widespread native, occ weedy spp. ..... .....
18) lvs copiously provided, at least marginally, with short, stout, blunt, subconic hairs, as well as us more or less stellate; boreal ..... northern h.w. (umbulatum) thickets, open woods & beaches; s to P?EI, NB disjunct to Spruce Knob, WV
18) lvs without subconic hairs, often stellate or long-hair or both ..... .....
19) invol bracts gradually tapering to a narrow but obtuse or rounded tip; plant 1.5-15dm; widespread ..... Canada h.w. (12.kalmii) woods, beaches & fields, esp in sandy soil; LB to NJ
19) invol bracts gradually tapering to a sharp point; plants 1-3.5dm; northeastern   northeastern h.w. (9.robinsonii) X