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Support the Flora of the Southeastern US

2024 has been a banner year for making the best flora we can imagine. We've created:
With financial support from people like you, we are aiming even higher in 2025. Together we can accomplish all this: Vote on our 2025 priorities
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Keyed in multiple places:

Click the number at the start of a key lead to highlight both that lead and its corresponding lead. Click again to show only the two highlighted leads. Click a third time to return to the full key with the selected leads still highlighted.

Key to Helianthus, Key A: sunflowers with basally disposed leaves

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1 Disk flowers yellow.
  2 Basal leaves 6-15 cm long, 2-8 cm wide; leaves 1.5-5× as long as wide, scabrous or hirsute (rarely glabrous)
    3 Leaves rough to touch, scabrous or hirsute; leaves entire or nearly so; [widely distributed]
    3 Leaves smooth to touch, strigose or glabrous; leaves usually serrate; [AR, LA, TX]
  2 Basal leaves 10-30 cm long, 0.5-2.0 cm wide; leaves 10-20× as long as wide, glabrous.
      4 Head 1 (-3); phyllaries 8-16 mm long, 3-5 mm wide; [of wet flatwoods and wet prairies of ne. FL]
      4 Heads 3-12; phyllaries 5-11 mm long, 1-2.5 mm wide; flowering Aug-Oct; [of sandstone and granite glades and woodlands and loamy to xeric longleaf pine sandhills; rarely escaped elsewhere]
1 Disk flowers red or purple (at least in part).
        5 Basal leaves 6-20 cm long; lower several pairs of stem leaves up to 1/2 as long and wide as the basal leaves; [collectively widespread in our region from VA, KY, IL, MO, and OK southwards, in the inland provinces and the Coastal Plain].
          6 Trichomes on the leaf abaxial midrib > 1 mm long; lower stem with a few pairs of leaves (< 8 nodes below the capitulescence), these strongly reduced upward; leaf blades (1.3-) 1.7-2.5 (-3)× as long as wide; petiole often > 1/3 as long as the blade, broadly winged toward the blade; plants to 2 m tall; nonflowering stems usually absent; [widespread in our area]
          6 Trichomes on the leaf abaxial midrib < 1 mm long; lower stem leafy, often to above the middle (> 8 nodes below the capitulescence); leaf blades 1-1.7 (-2)× as long as wide; petiole usually < 1/3 as long as the blade, narrowly winged toward the blade; plants to 3 m tall; nonflowering stems usually present; [west of our area]
        5 Basal leaves 4-15 cm long; lower several pairs of stem leaves often < 1/2 as long and wide as the basal leaves; [Coastal Plain, NC to FL to e. LA].
             7 Basal leaves (1.6-) 2-5× as long as wide; ray flowers present, 12-18, typically 1.5-3.5 cm long; [wet savannas and bogs]
             7 Basal leaves 1-1.5× as long as wide; ray flowers none, or present, 2-8, but < 1 cm long; [dry savannas and sandhills]

Key to Helianthus, Key D: perennial sunflowers with leafy stems and yellow disk flowers

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1 Stems below the capitulescence glabrous or nearly so, sometimes glaucous.
  2 Leaves whorled at principal nodes, either alternate or opposite at other nodes
  2 Leaves either alternate or opposite (or both), never whorled.
    3 Leaves grayish-green or bluish green in color, sessile, and glabrous and glaucous on the undersurface.
      4 Rays 10-14; leaves strumose adaxially, rough to the touch; phyllaries 3.5-4.5 mm wide
      4 Rays 5-10; leaves glabrous or glabrate adaxially, smooth or only slightly rough to the touch; phyllaries 2-3 mm wide
    3 Leaves light to dark green, sometimes whitish abaxially, but not grayish or bluish green in color; leaves sessile or petiolate, glabrous or pubescent.
        5 Leaves linear-lanceolate, with only a single main vein
        5 Leaves linear-lanceolate to lanceolate, lance-ovate, or ovate, triplinerved at base.
          6 Rays few, usually 5 or 8; heads small, the involucres 9 mm broad or less.
             7 Leaves abaxially whitish in color and glabrous and glaucous, lacking subsessile glandular trichomes (‘resin dots’)
             7 Leaves abaxially greenish in color, usually tomentulose (sometimes glabrate), with abundant subsessile glandular trichomes
          6 Rays usually 10 or more in larger heads; heads larger, the involucres usually > 9 mm broad.
               8 Leaves sessile, rounded to cordate at base, and trinerved, with the 2 lateral veins diverging from the midrib at the very base of the leaf
               8 Leaves sessile to petiolate, but narrowing gradually to base and triplinerved, the 2 lateral veins diverging from the midrib above the base of the blade.
                 9 Anther appendages yellow.
                   10 Leave blade lanceolate to lance-ovate, sessile to petiolate but the petiole usually < ¼ as long as the blade; phyllaries not conspicuously graduated and imbricate, usually loose and spreading
                   10 Leaf blade ovate to elliptic, with a distinct petiole usually > 2 cm long and ½ as long as blade or longer; phyllaries conspicuously graduated and imbricate, usually appressed, not exceeding disk
                 9 Anther appendages dark or reddish-brown.
                     11 Plants producing abundant tubers; leaves subsessile, the petioles < 1 cm long; [endemic to the Piedmont of NC and SC]
                     11 Plants rhizomatous, but not producing tubers; leaves petiolate, the petioles 1-5 cm long; [collectively widespread in our area].
                       12 Longer phyllaries usually exceeding disk by ½ their length or more, apex acuminate; larger leaves moderately to conspicuously serrate, with a petiole 2-5 cm long, and abaxially with usually relatively few subsessile glandular trichomes
                       12 Phyllaries equal to or slightly exceeding disk, apex acute; leaves moderately serrate to entire, with a petiole 1-3 cm long, and abaxially with usually abundant subsessile glandular trichomes (‘resin dots’)
1 Stems pubescent throughout, not glaucous.
                          13 Leaves sessile and cordate, mostly or all opposite
                          13 Leaves petiolate or sessile, but not cordate, and alternate or opposite.
                            14 Phyllaries attenuate, conspicuously exceeding the disk in length and reflexed, apically with numerous subsessile glandular trichomes (‘resin dots’); leaf bases often convex, the basically ovate or lance-ovate blade joined to a broadly winged and gradually narrowed petiole
                            14 Phyllaries acute to attenuate, but not reflexed, subsessile glandular trichomes present or absent; leaf bases usually attenuate to truncate or rounded, the blade lance-linear or lanceolate, or if ovate or lance-ovate either sessile or with a petiole that is at most narrowly winged.
image of plant
Show caption*© Gary P. Fleming
                              15 Leaves conduplicate (strongly folded along the midvein, thus V-shaped) and entire, usually with only a single prominent main vein; inflorescence when well developed spiciform or racemose
                              15 Leaves not conduplicate, entire or serrate, triplinerved (with a prominent lateral pair of veins near the base); inflorescence not spiciform or racemose.
                                16 Phyllaries conspicuously graduated and imbricate, usually appressed.
image of plant
Show caption*© Michael J. Oldham, some rights reserved (CC BY-NC), uploaded by Michael J. Oldham
                                  17 Leaf blades lanceolate to ovate, petiole 1-5 cm long and usually < ½ as long as blade; anther appendages with dark pigment; cypselas 4-5 mm, usually sterile
                                  17 Leaf blades ovate to elliptic, petiole distinct, > 2 cm and usually > ½ as long as the blade; anther appendages yellow; cypselas 3-4 mm long, fertile
                                    18 Leaves rough to touch, scabrous or hirsute; leaves entire or nearly so; [widely distributed]
                                    18 Leaves smooth to touch, strigose or glabrous; leaves usually serrate; [w. LA, AR, TX]
                                16 Phyllaries not conspicuously graduated and imbricate, usually loose or spreading.
                                       19 Leaves with a prominent petiole > 2 cm long, blades lance-ovate to ovate and > 5 cm broad; cypselas 5-7 mm long; tubers produced late in growing season
                                       19 Leaves sessile or with a short petiole usually < 2 cm long; blades linear to lanceolate, < 4.5 cm broad; cypselas 3-5 cm long; tubers present or absent.
                                         20 Leaves truncate to broadly rounded at base, shortly but distinctly petiolate
                                         20 Leaves cuneate, gradually narrowing to base, sessile to petiolate.
                                           21 Ligules lacking subsessile glandular trichomes; leaves not strongly revolute
                                           21 Ligules abaxially with subsessile glandular trichomes (‘resin dots’); leaves usually revolute.
                                             22 Heads relatively small, the discs usually < 15 mm across; tubers present
                                             22 Heads larger, the discs (at least the larger) > 15 mm across; tubers absent.
                                               23 Leaves conspicuously undulate; ovate to elliptical to lanceolate, occasionally linear (if so, usually < 10 cm long), usually < 5× as long as wide; heads 1-6 per plant; outer phyllaries acute to obtuse
                                               23 Leaves not conspicuously undulate; linear to lanceolate, > 5× as long as broad (and also 8-16 cm long); heads 3-16 per plant; outer phyllaries acuminate to acute.
                                                 24 Plants short, < 1.5 m tall; leaves < 1 cm wide; rhizomes lacking or poorly developed
                                                 24 Plants robust, > 1.5 m tall; leaves > 1 cm wide; rhizomes well developed