Rohan Wells, National Institute of Water & Atmospheric Research, Bugwood.org

Family: Hydrocharitaceae (Tape-Grass Family)

Synonym(s):

Duration: Perennial

Habit: Herb

Listed by:
Invasive Plant Atlas of the US: 1
Federal Noxious Weed: 1
TDA Noxious Weed: 1
TPWD Prohibited Exotic Species: 1

Description: Lagarosiphon major is a perennial, submerged, aquatic plant. It has many thread-like roots, which are 'adventitious' (branching from the stem) and, along with rhizomes (horizontal stems in the sediment), anchor it to the bottom. Stems that can reach the surface, are brittle and sparsely branched, 3-5mm in diameter and J-shaped. The leaves are 5-20mm long and 2-3mm wide, and occur in alternate spirals along the stem.The female flowers are 3-petaled, very small, clear-white on the surface, and grow on very thin, whitish, filament-like stalks.

History: Not introduced to the United States. Declared as a Federal Noxious Weed in 2006. Spread through the world by the aquarium trade.

Biology & Spread: Lagarosiphon major is very difficult to control, and its ability to form new plants vegetatively facilitates its spread to new locations. The trade and potential escape of L. major through the aquarium and water garden industry plays a large role in its spread to new locations, as does the transportation of this plant on recreational equipment moving between water bodies (Cronk and Fuller, 1995). Other species of the family Hydrocharitaceae also have the potential to become invasive, and Elodea canadensis, Egeria densa, and Hydrilla verticillata, have been recorded as problematic outside of their native range.

Ecological Threat: The English common name 'oxygen weed' refers to the species ability to 'oxygenate' the water, however, the dense mats of vegetation that are characteristic of this species when introduced outside of its native range actually decrease the oxygen levels by limiting water circulation and increasing decomposition.
Lagarosiphon major is fast-growing, may totally fill the volume of a large shallow lake (to 3 m deep, fills water control channels.

US Habitat: lakes, riparian zones, water courses, wetlands

Distribution

US Nativity: Not in the U.S.

Native Origin: Native in southern Africa

US States: As of 2023, Lagarosiphon major does not yet occur in the wild in the United States; partly due to Early Detection efforts at a Federal and State level. However, experts believe should this plant be introduced to the U.S., the resulting problems could be as consequential as hydrilla (Hydrilla verticillata) an infamous invasive also in the Hydrocharitaceae family.

Resembles/Alternatives:

Management:

USE PESTICIDES WISELY: ALWAYS READ THE ENTIRE PESTICIDE LABEL CAREFULLY, FOLLOW ALL MIXING AND APPLICATION INSTRUCTIONS AND WEAR ALL RECOMMENDED PERSONAL PROTECTIVE GEAR AND CLOTHING. CONTACT YOUR STATE DEPARTMENT OF AGRICULTURE FOR ANY ADDITIONAL PESTICIDE USE REQUIREMENTS, RESTRICTIONS OR RECOMMENDATIONS. MENTION OF PESTICIDE PRODUCTS ON THIS WEB SITE DOES NOT CONSTITUTE ENDORSEMENT OF ANY MATERIAL.

Listing Source

Texas Department ofAgriculture Noxious Plant List
Texas Parks and Wildlife Department Prohibited Exotic Species
Invaders Program
Federal Noxious Weed
Union of Concerned Scientists
United States Forest Service Southern Research Station

Text References

Center for Aquatic Invasive Plants. 2009. African elodea. University of Florida. Accessed 19 August 2010 (http://plants.ifas.ufl.edu/node/220).

Bickel, T.O. 2011. Lagarosiphon major (Ridley) Moss ex Wager (Curly Water Weed). In: Francis, R.A. (Ed.). A Handbook of Global Freshwater Invasive Species (1st ed.). Routledge.

Data Source

https://www.invasivespeciesinfo.gov/aquatic/plants/oxygen-weed

Last Updated: 2024-02-05 by ARMO, TISI