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How did 'elodea' spread without females?

By Chelsie Vandaveer

June 26, 2003

killerPlants Tendrils: ~~1~~2~~3~~4~~5~~

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Suggested Reading—>Click here.

Assorted Killer Savings Garden Links—>Click here.

Killer Picks: Wollemi Pine, greatest living fossils discovered in the 20th century—>Click here.

Global Travel Jacket, Earth Explorer Shoulder Bag, Men's Leather Travel Shoes—>Click here.

Indian Tapestry Woven Jacket, Bolivian Manta & Leather Backpack—>Click here.

Women's Maori Fern Travel Shoes—>Click here.

Brazilian waterweed (Egeria densa Planchon) is a common plant known to aquaria hobbyists. Native to South America, it was first found growing in Long Island in the late 1800s. In the early 1900s, the plant entered commerce--sold in pet shops under the names 'elodea' and 'anacharis'. In days before air pumps, the plant served to keep aquarium water oxygenated for the fish. The plant has become a nuisance where it has been introduced in lakes and waterways. In the U.S., it is now found in thirty-three states.

Brazilian waterweed will grow whether rooted in the mud or floating free at the water's surface. Given sufficient light and space, the brittle stems grow to lengths of five or more meters (16+ feet). Thick mats of waterweed make swimming, water skiing, boating, and fishing close to impossible. Free-floating stems clog intakes at hydroelectric plants and shade out native vegetation in the water. ("Brazilian Elodea", Washington State Department of Ecology)

Brazilian waterweed (Egeria densa Planchon) was named for a nymph,
a nature spirit worshipped by the ancient Sabines
in the early years of the Roman Empire.
Landscape with the Nymph Egeria Framed Art Print by Claude Lorrain
Buy Framed Art Print at AllPosters.com

Waterweed has whorled leaves, usually four at each node. But about every eight or ten nodes, the stem has a double-node, a place where the stem did not elongate between the whorls of leaves. (The double-nodes are identified by the six to nine leaves.) Waterweed will only branch or root at these double-nodes.

Brazilian waterweed is dioecious, staminate (male) and pistillate (female) flowers are borne on separate plants. In summer, waterweed flowers--three white petals floating on the water. Pollination is by insects visiting the flowers. (Flowering Plant Families, Wendy B. Zomlefer, University of North Carolina Press, 1994)

In the many places where the plant has become a nuisance (North America, Hawaii, New Zealand, and other places), no female plants or seeds have been found. And no one really knows why. Waterweed has spread entirely by pieces of the male plants intentionally or inadvertently carried there.

The Age of Aquariums has a photograph and great page about Egeria densa use in aquariums. To view the photograph, click on the link:

http://www.aquahobby.com/garden/pegeria.html

University of Florida, Center for Aquatic and Invasive Plants has photographs of Egeria densa and a link to "Aquatic Weed Fact Sheet: Brazilian Elodea or Egeria, NC State University" for more environmental information. To view the photograph, click on the link:

http://plants.ifas.ufl.edu/egdepic.html

killerPlants Tendrils: ~~1~~2~~3~~4~~5~~

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National Geographic®

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National Geographic®

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Shop the National Geographic Store. All purchases support research and education.

Bolivian Manta and Leather Backpack

National Geographic®

Using a centuries-old technique, Bolivian families weave mantas—woolen textiles in geometric patterns—for bedding and apparel. Today, artisans frame vintage and contemporary mantas in durable hand-tooled leather to give them new life in these travel-friendly bags. The chocolate brown leather strap can be worn over one shoulder or unzipped to wear as a backpack, and the sides unsnap to expand capacity.

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Women's Maori Fern Travel Shoes

National Geographic®

A comfortable, sturdy pair of shoes that can stand up to long days of sightseeing as well as evenings on the town is a must for any traveler. Hand-stitched in Israel, these Mary Jane–style flats from Naot have an orthopedist-recommended removable cork/latex memory-foam foot bed that molds to your foot for customized arch support and shock absorption. Breathable leather uppers and adjustable hook-and-loop straps add flexibility and comfort.

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Shop the National Geographic Store. All purchases support research and education.

Wollemi Pine

National Geographic®

Exclusively from National Geographic, this survivor from the age of the dinosaurs is one of the greatest living fossils discovered in the 20th century. The Wollemi pine is one of the world's oldest and rarest tree species, belonging to a 200-million-year-old plant family thought to have been extinct for more than two million years.

Previously known only from fossil records, it was presumed extinct until a single tree was found in the Wollemi National Park, Australia, in 1994. Subsequent research discovered 100 adult trees that have survived in a single canyon in this wild and rugged area. Click here to view canyon, trees and fossil record.

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Comes with a care manual with the full story about the discovery and fascinating history of the Wollemi pine. Comes in a copper-colored container and will be approximately 10''H when shipped. A portion of the proceeds from the sale of these plants will fund ongoing conservation research. Click here to get your Wollemi Pine and assist in the conservation effort.

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National Geographic®

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