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Key to Thalictrum

Ranunculaceae

Thalictrum

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1 Sepals petaloid, conspicuous, white (or tinged with pink or green); leaflike involucral bracts present, opposite or whorled; inflorescence an umbel; [section Anemonella]
1 Sepals absent, or inconspicuous in comparison to the stamens or pistils; leaflike involucral bracts not present; inflorescence a panicle, corymb or raceme.
  2 Fruit (achene) scimitar-shaped, borne on a stipe 1.5-4 mm long; flowers perfect; [section Physocarpum].
    3 Achene concave or straight on the upper surface, 4-5.5 mm long, borne on a stipe 1.5-3 mm long; inflorescence branches stiff and diverge at acute angles; [fairly widespread in our area, on a wide variety of moist substrates, especially in the Mountains]
    3 Achene straight on the upper surface, 2.5-4 mm long, borne on a stipe 2.5-4 mm long; inflorescence branches flexuous and divergent; [of sandstone rockhouses of Cumberland Plateau of AL, TN, and KY]
  2 Fruit (achene) not scimitar-shaped, not borne on a stipe (except T. coriaceum); flowers unisexual (or sometimes a few or more bisexual).
      4 Leaflets of the stem leaves linear to narrowly lanceolate, oblanceolate or elliptic, (3-) 5-10 (-25)× as long as wide; [section Leucocoma]
      4 Leaflets of the stem leaves ovate, obovate, or suborbicular, 0.7-3 (-5)× as long as wide.
        5 Most of the leaflets with (3-) 4-6 (-9) lobes or teeth; [section Heterogamia].
          6 Cauline leaf subtending the lowest flowering branch sessile; plant flowering May-Jul; achenes borne on a 0.7-2.5 mm long stipe
          6 Cauline leaf subtending the lowest flowering branch with a petiole 3-7 cm long; plant flowering Mar-Apr; achenes nearly sessile, the stipe nonexistent or <0.3 mm long.
             7 Largest leaflets > 15 mm long; stems 30-80 cm tall, erect
             7 Largest leaflets < 15 mm wide; stems 10-40 (-45) cm tall, reclining or erect.
               8 Achenes 0.7-1.2 mm thick, with 6-8 veins; achene beak 1.3-3.0 mm long; [GA west to MS; east of MS river]
               8 Achenes 1.4-2.0 mm thick, with 6-8 veins (T. texanum) or 10-12 veins (T. arkansanum); achene beak 1.3-3.0 mm long; [AR, OK, TX; west of MS river].
                 9 Plants reclining; stigmas 1.3-3 mm long; achenes ellipsoid; roots brown when dry; [ne. TX, adjacently in OK and AR]
                 9 Plants erect; stigmas 0.5-1 mm long; achenes ovoid; roots black when dry; [se. TX]
        5 Most of the leaflets with 1-3 (-5) lobes or teeth; [section Leucocoma].
                          13 Leaflet undersurfaces, peduncles, and achenes glabrous to glabrate (rarely all three in T. pubescens, but keyed below as a fail-safe).
                            14 Leaflets entire to 3-lobed, averaging about 10 mm wide, the broadest usually < 20 mm wide; filaments (2-) 3-4.5 (-6.5) mm long (averaging 3.6 mm)
                            14 Leaflets 3-lobed (rarely entire), averaging 15-23 mm wide, the broadest usually (5-)15-60 (-70) mm wide; filaments (1.5-) 4-5 (-8) mm long (averaging 4.5 mm).
                                16 Leaflets and achenes lacking stipitate glands or papillae; filaments somewhat to prominently dilated distally (clavate); achenes often with a coiled beak (sometimes straight)

Key to Ranunculaceae, Key C: Subkey in Ranunculaceae

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1 Leaflets linear, < 1.5 mm wide.
  2 Flowers bilaterally symmetrical; [subfamily Ranunculoideae, tribe Delphineae]
  2 Flowers radially symmetrical.
    3 Aquatic; [native]; [subfamily Ranunculoideae, tribe Ranunculeae]
    3 Terrestrial; [exotic].
      4 Flower closely subtended by a finely dissected involucre; pistils compound; [subfamily Ranunculoideae, tribe Nigelleae]
      4 Flower lacking involucre; pistils simple.
        5 Petals 8-15 mm long, red, purple, or orange; [subfamily Ranunculoideae, tribe Adonideae]
        5 Petals 3-5 mm long, yellow; [subfamily Ranunculoideae, tribe Ranunculeae]
1 Leaflets broader, rounded, lobed, or toothed.
          6 Leaves all cauline, opposite; stems somewhat woody at base; [subfamily Ranunculoideae, tribe Anemoneae]
             7 Petals present, conspicuous
               8 Flowers dangling; petals red, orange with yellow, or blue, spurred; [subfamily Thalictroideae]
               8 Flowers not dangling; petals yellow, not spurred; [subfamily Ranunculoideae, tribe Ranunculeae]
             7 Petals absent or inconspicuous (soon deciduous or altered into a nectary-bearing clavate structure); sepals sometimes petaloid and conspicuous.
                 9 Sepals petaloid, conspicuous, white (or cream, rose, pink, or tinged with green).
                   10 Involucre absent, all leaves on the stem alternate; petaloid sepals 5, white; [subfamily Thalictroideae]
                   10 Involucre of opposite or whorled, leaflike bracts present; petaloid sepals (4-) 5-20 (-30), white, cream, rose, or green.
                     11 Basal leaves with 3-5 leaflets, these toothed or incised; petaloid sepals white, cream, rose, or green; [subfamily Ranunculoideae, tribe Anemoneae]
                     11 Basal leaves with > 5 leaflets; these with 0-3 rounded lobes at the tip; petaloid sepals white to pale pink; [subfamily Thalictroideae]
                 9 Sepals absent, or inconspicuous in comparison to the stamens or pistils.
                       12 Leaflets 3; flower solitary; [subfamily Coptidoideae]
                          13 Inflorescence a raceme; [subfamily Ranunculoideae, tribe Cimicifugeae]

Key to Ranunculaceae, Key D: Subkey in Ranunculaceae

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1 Fruit a follicle or capsular (or fleshy and berrylike in some Actaea).
  2 Mature leaves > 4 dm wide; [subfamily Ranunculoideae, tribe Cimicifugeae]
  2 Mature leaves < 3 dm wide.
      4 Flowers in a raceme, not subtended by an involucre; fruit follicular, each with a 1-2 mm long beak; [subfamily Ranunculoideae, tribe Delphineae]
      4 Flower solitary, subtended by a finely divided involucre; fruit a spherical capsule-like structure composed of 5 or 10 partially connate follicles, each follicle terminated by a linear beak 13-20 mm long; [subfamily Ranunculoideae, tribe Nigelleae]
    3 Leaflets broad, rounded; [mostly natives].
        5 Follicles borne on stipes, forming an umbel-like cluster; rhizomes yellow or orange; [subfamily Coptidoideae]
        5 Follicles sessile; rhizomes brown or tan; [subfamily Thalictroideae].
          6 Follicles 15-31 mm long, with beaks 7-18 mm long
          6 Follicles 3.5-6.5 mm long, with beaks 1.5-3 mm long
1 Fruit an achene.
             7 Leaves divided into numerous linear segments, all of which are < 1 mm wide.
               8 Plant aquatic (if leaves divided into numerous linear segments); [subfamily Ranunculoideae, tribe Ranunculeae]
               8 Plant terrestrial.
                 9 Achenes 3-5 mm long, glabrous, with a persistent beak 0.5-1 mm long; [subfamily Ranunculoideae, tribe Adonideae]
                 9 Achenes 1.6-2 mm long, tomentose, with a persistent beak 3.5-4.5 mm long; [subfamily Ranunculoideae, tribe Ranunculeae]
             7 Leaf segments rounded or cleft, > 1 mm wide.
                   10 Leaves cauline, opposite; [subfamily Ranunculoideae, tribe Anemoneae]
                   10 Leaves basal and/or cauline, cauline leaves (if present) alternate (leaflike involucral bracts sometimes present and opposite or whorled).
                       12 Achenes not ribbed or veined on lateral surfaces; leaf texture moderate to distinctly thick and leathery; [subfamily Ranunculoideae, tribe Anemoneae]
                       12 Achenes conspicuously ribbed or veined on lateral surfaces; leaf texture thin, delicate; [subfamily Thalictroideae]
                          13 Leaflets 3-many, if many the leaflets typically with teeth, or sharp lobes; [subfamily Ranunculoideae, tribe Ranunculeae]
                          13 Leaflets many, unlobed or typically with 3-9 rounded lobes; [subfamily Thalictroideae]