Bladderwort Family
Utricularia
1 Flowers white or cream-white, 1-3mm long; inflorescence peduncles very reduced, pedicels appearing to arise directly from stolons;traps 0.3-0.8mm long; plants floating unattached in water (sometimes deposited on land by dropping water, but then principal branch
systems stranded on soil surface); capsules ca.1mm long, fusiform, indehiscent, with 1 seed; seeds essentially smooth, unornamented;
leaves absent ........................................................................................................................................................... Piedmont Bladderwort
1 Flowers yellow, pink, or purple (sometimes fading whitish), (2-)5-20mm long; inflorescence peduncles well-developed, inflorescence
clearly a raceme; traps 0.2-5.0mm long (< 0.7mm long only in terrestrial species (see key lead 2); plants attached (with principal branch
systems within soil), or floating unattached in water (sometimes deposited on land by dropping water, but then principal branch systems
stranded on soil surface); capsules 1-8mm long, globose, subglobose, or ovoid, with many seeds; seeds reticulate, papillose, echinate, multi-
angled, or winged (rarely more-or-less smooth); leaves present (sometimes absent in terrestrial species).
2 Plants attached (principal branch systems within soil); leaves absent or simple, linear, grass-like aerial leaves; bladders 0.2-1.1mm long,
most or all on plant usually < 1.0mm long; seeds reticulate-alveolate (also angled in Lavender Bladderwort), 0.20-0.25mm long.
3 Flowers pink; inflorescence 1(-2)-flowered; bract at base of pedicel tubular, attached circumferentially around stem; aerial leaves (when
present) terete, septate ....................................................................................................................................... Lavender Bladderwort
3 Flowers yellow (sometimes fading whitish); inflorescence (1-)2-15-flowered; bract at base of pedicel peltate or ovate, attached on one
side of stem; aerial leaves (when present) flattened, not septate.
4 Bracts subtending the pedicels peltate (attached near their middles), unattached at either end; pair of bracteoles absent; spur of the
corolla oriented forward, more-or-less appressed to the lower lip; aerial leaves (when present) with subacute to obtuse apex........
................................................................................................................................................................................... Zigzag Bladderwort
4 Bracts subtending pedicels ovate (attached at their bases), free only at their upper end; pair of bracteoles associated with each bract
present, linear to lanceolate; spur of corolla oriented downward or backward, at approximately a right angle to lower lip; aerial leaves
(when present) with acute apex.
5 Corolla 1.5-2.0cm long; spur 8-12mm long; raceme usually short, the (1-)2-6 flowers crowded together, all of them eventually
opening fully ..................................................................................................................................................... Horned Bladderwort
5 Corolla 0.25-1.5cm long; spur 5-7(-9)mm long; raceme usually elongate, the (1-)2-15 flowers well-spaced, often the lower (sometimes
all) remaining closed and much smaller than the fully opening flowers .............................................................Rush Bladderwort
2 Plants floating unattached in water (sometimes deposited on land by dropping water, but then principal branch systems stranded on soil
surface); leaves present and dissected into linear segments; bladders 0.7-5.0mm long, most or all on a plant > 1.0mm long; seeds
papillose, reticulate, ridged, angled, or winged, 0.5-2.0mm long.
6 Flowers purple; leaves divided into verticillate segments with terminal traps ....................................... Eastern Purple Bladderwort
6 Flowers yellow; leaves divided into alternate segments with lateral traps.
7 Peduncle with whorl of inflated leaf-like organs (floats).
8 Floats 4-7, not fused basally to one another, fusiform, tapering gradually to base and apex from a widest point near the middle;
leaves with the 2 primary divisions unequal; bracts of the scape longer than broad, entire; flowers (6-) 9-14 (-17) per scape; apex
of corolla spur bifid ......................................................................................................................................... Swollen Bladderwort
8 Floats (5-) 6-8 (-10), fused basally to one another, cylindrical, more-or-less parallel-sided through most of their length, tapering
abruptly to base and apex; leaves with the 2 primary divisions equal; bracts of the scape broader than long, the apex slightly to
strongly 3-lobed; flowers (1-)3-4(-7) per scape; apex of corolla spur usually entire (rarely bifid) .............. Floating Bladderwort
7 Peduncle without whorl of inflated leaf-like organs (floats).
9 Lower lip of corolla 3-lobed; seeds disk-shaped, not angular or winged; inflorescences of 2 types, open flowers on erect
peduncles 5-25 cm long bearing 2-8 flowers, closed flowers without a peduncle, the solitary pedicels borne directly on the stolons,
0.5-2cm long, deflexed ...................................................................................................................... Hidden-fruited Bladderwort
9 Lower lip of corolla entire or slightly irregular, not 3-lobed; seeds angular or winged; inflorescences of all erect, open flowers.
10 Upper corolla lip smaller than lower, entire; ripe seed pod splitting around middle; seeds 0.7-1.0mm long, 4-6-angled; corolla
without stipitate glands on its external surface.
11 Leaves of one kind only, divided into numerous capillary segments bearing lateral traps; bracts scarcely auriculate; plant
distinctly aquatic, floating in water and only rarely stranded.............................................................. Common Bladderwort
11 Leaves of 2 or 3 kinds, some divided into capillary or narrowly linear segments and bearing few or no traps, others divided
into fewer capillary segments and bearing more-or-less numerous traps; bracts distinctly auriculate; plants typically in boggy
situations, in shallow water or frequently stranded.
12 Broadest leaf segments with 9-20 lateral setae (use 10× magnification); spur of corolla cylindrical, distinctly longer than
wide, the apex distinctly curved forward ...................................................................................... Flat-leaved Bladderwort
12 Broadest leaf segments lacking lateral setae; spur of corolla shortly saccate to broadly conical, wider than long, the apex
not curved forward ................................................................................................................................. Lesser Bladderwort
10 Upper corolla lip larger than lower, obscurely 3-lobed; capsule laterally 2-valved or indehiscent; seeds 0.8-2.5mm long,
lenticular, with irregular, lobed, or continuous wing; corolla (or at least spur) with few to many short stipitate glands.
13 Vegetative shoots uniform, all bearing rather sparsely divided leaf segments bearing traps, seeds 0.8-1.1mm long, with a
continuous, circumferential wing, slightly to irregularly lobed ..............................................................Humped Bladderwort
13 Vegetative shoots of 2 kinds, some bearing leafy segments and few or no traps, others bearing reduced segments and more-
or-less numerous traps; seeds 1.0-2.5mm long, with an irregularly deeply lobed or partial wing........... Striped Bladderwort