Nelumbo lutea Willd.

American Lotus

© SRTurner

Family - Nelumbonaceae

Habit - Perennial aquatic forb, with milky latex and extensive, branching, spongy rhizomes, rooting at the nodes and bearing large, banana-shaped tubers (produced in autumn).

Stems - Aerial stem absent.

Leaves - Spirally alternate, mostly long-petiolate, the petiole smooth, to 3 m or more, relatively stiff and stout, reaching the water surface or emergent to about 80 cm. Stipules apparently absent, but perhaps represented by small, sheathing scales at the petiole bases. Leaf blades to 60 cm in diameter, centrally peltate, circular, the margin entire but slightly undulate, the upper surface flat (in floating blades) to moderately concave (in emergent blades) about the central attachment point (visible as a pale, scarlike mark), glabrous, often somewhat glaucous, the undersurface pale but with small brown spots, the main veins numerous, palmate from the petiolar attachment, mostly branched dichotomously 2 or more times, raised on the blade undersurface, connected by a network of finer crossveins.

	Leaves, dorsal view.
© SRTurner

	Leaves, lateral view.
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	Leaf upper side.
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	Leaf lower side.
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	Leaf lower surface.
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	Channeled petiole. The aerenchymatous tissue facilitates gas exchange between the atmosphere and submerged plant tissues.
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	Petiolar strands of solidified latex or vascular vessels?
© SRTurner

Inflorescences - Solitary flowers, these long-stalked directly from the nodes of the rhizome, emergent and usually slightly overtopping the emergent leaves.

Flowers - Hypogynous, perfect, actinomorphic. Perianth showy, creamy to pale yellow, of numerous, spirally arranged, overlapping tepals; the outermost 3-5 tepals 0.8-1.4 cm long, often green or greenish-tinged; grading into the median tepals, these 7-12 cm long, obovate; grading into the innermost ones, these somewhat shorter, lanceolate, grading into the stamens. Stamens numerous, arranged in a dense, overlapping spiral, the filament 6-12 mm long, slender, the anther 9-18 mm long, attached at the base, orangish yellow, with a terminal appendage 3-5 mm long. Pistils 8-32, simple, free from one another, embedded in deep pits along the upper surface of a large, flat-topped, conic, spongy, expanded receptacle, this continuing to expand as the fruits mature, becoming nodding, dark brown, enlarged to 10 cm, and somewhat leathery to hardened at fruiting. Style 1 per ovary, very short, the stigma protruding through an apical pore in the receptacle pit, more or less disc-shaped, slightly concave and with a central pore. Ovule 1 per carpel, the placentation apical.

	Flower.
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	Receptacle.
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Fruits - Aggregate fruits consisting of nuts embedded in the long-persistent, greatly expanded receptacle. Nuts 9-16 mm long, nearly spherical, indehiscent, hard-walled, brown to nearly black.

	Immature fruits.
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	Mature fruits.
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	Fruit and nuts.
© SRTurner

Flowering - June - September.

Habitat - Lakes, ponds, sloughs, marshes.

Origin - Native to the U.S.

Lookalikes - None.

Other info. - This strikingly bizarre species is probably found throughout Missouri, although it is under-documented by voucher due to its large size and aquatic habitat. Its range includes the eastern half of the continental U.S., though most commonly in the Midwest, and also Mexico and Central America. It is easily recognized by its large, circular, peltate leaves and large flowers, and later by the strange fruiting receptacles. These fruiting heads have been used in dried flower arrangements.

The flowers of this species are unique among the native Missouri flora, having large, conical receptacles which become further enlarged during maturation to produce the bizarre-looking fruiting heads. In the flowering season, this receptacle is thermogenic, maintaining the flower at a constant 31°C regardless of ambient temperature. This warmth serves to enhance emission of volatile aromatic compounds produced in the flower tissues. The function of the stamen appendages is unknown but may have once served to attract a specific pollinator.

Lotus has a long history of cultivation as an aquatic ornamental, although it can grow very aggressively and quickly overwhelm small ponds. A 45-foot radial enlargement of one population during a single growing season has been documented, and a single rhizome can reach 90 feet or more in length. Lotus is edible, although care should be exercised in collecting wild plants because these sometimes carry parasites from the mud and water in which they are growing. A related species, L. nucifera ("sacred lotus"), is grown commercially as a food crop, mainly for the rhizome and seeds. Asian grocery stores will often carry "lotus root" for use as a vegetable. Lotus seeds may remain viable for over 1,000 years.

	Section of "lotus root" (actually rhizome, probably from L. nucifera) for use as a vegetable, from international grocery store.
© SRTurner

Photographs taken at Busch Wildlife Area, St. Charles County, MO, 06-28-2009, 07-27-2011, and 06-29-2012, Shaw Nature Reserve, Franklin County, MO, 10-11-2016, and Glassberg Conservation Area, Jefferson County, MO, 6-28-2023 (SRTurner).