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fleur-de-lis, horticultural iris, iris jaune, pale-yellow iris, yellow flag, yellow iris, yellow water iris

dwarf lake iris

Rhizomes

pink, freely branching, producing extensive clumps, 2–3 cm diam., with fibrous remains of old leaves;

roots fleshy.

with proximal cordlike portion 0.8–2 dm × 2 mm, bearing brown, scalelike leaves and rarely roots, distal portion enlarging to 3–5 × 0.8–1.2 cm, producing fibrous roots, 2–3 brown, sheathing, bractlike leaves, then 8–12 green foliage leaves; usually 2 cordlike rhizomes produced from apex as new growth begins in spring.

Stems

usually 1-branched, solid, 7–15 dm.

simple, 0.8–4 cm.

Leaves

basal deciduous, at first erect, then recurved, blade dark green, with prominent median thickening, 4–10 dm × 2–3 cm, slightly glaucous basally;

cauline equaling inflorescence unit.

basal with blade broadly linear at anthesis, slightly falcate, 4–6 cm × 6–8 mm, enlarging to 16 cm × 10 mm;

cauline with proximal 1–2 resembling basal leaves, 4–6 cm, distal 2 more sheathing of stem, exceeding spathes.

Inflorescence units

4–12-flowered;

spathes green with brown margins, outer spathe strongly keeled, inner without keel, 6–9 cm, subequal, margins not scarious.

1(–2)-flowered;

spathes green, outer closely sheathing inner and enclosing ovary, slightly keeled at midrib, 4.5 cm, ± equal, margins scarious.

Flowers

perianth bright yellow;

floral tube 0.6–0.8 cm, with no constriction into ovary;

sepals bright yellow or cream colored, lanceolate to ovate or suborbiculate, 5–7.5 × 3–4 cm, base abruptly attenuate, claw ca. 1/2 length of limb, signal a darker yellow basal patch limited by short, brown lines;

petals without veining, lanceolate to spatulate, 2–3 cm;

ovary triangular in cross section with concave sides and narrow groove at each angle, 1.5 cm;

style keeled, 3–4 cm, crests spreading, 1–1.2 cm, laciniate at apex;

stigmas rounded with prominent tongue;

pedicel 2.5–7 cm.

perianth sky blue;

floral tube dull yellow, funnelform, 1–2 cm, dilated upward to 4–5 mm diam.;

sepals 2–2.3 × 0.8 cm, tapering gradually into claw, apex emarginate, signal white with deep violet margin, with 3 yellow and white, toothed, low ridges;

petals spreading, narrowly oblanceolate, 1–1.5 × 0.4–0.5 cm, shorter and narrower than sepals, apex emarginate;

ovary sharply trigonal, 0.8–1 cm;

style 1–2 cm, crests linear to semiovate, 4 mm, margins crenate;

stigmas rounded, margins entire;

pedicel 0.6–1.5 cm.

Capsules

prismatic to oblong-ovoid, obscurely 3-angled with obvious groove at each angle, 3.5–6 cm, beak 5 mm.

roundly triangular, 1.2 × 8 mm, enclosed in spathes.

Seeds

D-shaped, flattened, 6–7 mm, corky, lustrous.

dark brown, with white appendage spiraled around seed, ca. 3 mm, quickly drying when exposed to air.

2n

= 34.

= 32, 42.

Iris pseudacorus

Iris lacustris

Phenology Flowering Apr–Jun. Flowering May.
Habitat Swamps, wet shores of rivers and lakes Moist, sandy gravel, limestone shores of lakes
Distribution
from FNA
AL; AR; CA; DC; DE; FL; GA; IA; IL; IN; KS; KY; LA; MA; ME; MS; NC; NH; NY; OH; PA; RI; SC; TN; VA; WA; WV; BC; MB; NB; NF; NS; ON; PE; QC; Eurasia; n Africa [Introduced in North America]
[WildflowerSearch map]
[BONAP county map]
from FNA
MI; WI; ON
[BONAP county map]
Discussion

Several authors have described Iris lacustris simply as being very similar to I. cristata, but smaller in every detail. W. R. Dykes (1913) said, “This name may be retained as that of a local form or variety but it hardly deserves specific rank.” He treated the taxon as I. cristata var. lacustris. R. C. Foster (1937) discussed the relationship between I. cristata and I. lacustris in detail, and recognized the latter at specific rank. He stated, “It is interesting to note that it has been recorded in several localities on or near the Bruce Peninsula, Ontario, that home of so many pre-Wisconsin relics. Professor Fernald informs me that he has seen it growing there in some abundance on the upper levels of the sandy beaches. Quite probably, it is present there, not as a newcomer, but as a relic.” However, G. L. Hannan and M. W. Orick (2000) concluded that I. lacustris is a product of some post-glacial invasion or introduction of a plant or seed of I. cristata that has developed its own very stable and quite unvariable character.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 26, p. 390. FNA vol. 26, p. 378.
Parent taxa Iridaceae > Iris > subg. Limniris > sect. Limniris > ser. Laevigatae Iridaceae > Iris > subg. Limniris > sect. Lophiris
Sibling taxa
I. bracteata, I. brevicaulis, I. chrysophylla, I. cristata, I. douglasiana, I. fernaldii, I. fulva, I. germanica, I. giganticaerulea, I. hartwegii, I. hexagona, I. hookeri, I. innominata, I. lacustris, I. longipetala, I. macrosiphon, I. missouriensis, I. munzii, I. orientalis, I. pallida, I. prismatica, I. pumila, I. purdyi, I. savannarum, I. setosa, I. sibirica, I. tenax, I. tenuis, I. tenuissima, I. tridentata, I. verna, I. versicolor, I. virginica
I. bracteata, I. brevicaulis, I. chrysophylla, I. cristata, I. douglasiana, I. fernaldii, I. fulva, I. germanica, I. giganticaerulea, I. hartwegii, I. hexagona, I. hookeri, I. innominata, I. longipetala, I. macrosiphon, I. missouriensis, I. munzii, I. orientalis, I. pallida, I. prismatica, I. pseudacorus, I. pumila, I. purdyi, I. savannarum, I. setosa, I. sibirica, I. tenax, I. tenuis, I. tenuissima, I. tridentata, I. verna, I. versicolor, I. virginica
Synonyms I. cristata subsp. lacustris, I. cristata var. lacustris
Name authority Linnaeus: Sp. Pl. 1: 38. (1753) Nuttall: Gen. N. Amer. Pl. 1: 23. (1818)
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