Identification: According to Ohwi (1965) and Wu and Larsen (2000): Habit: emergent aquatic, perennial forb
Stems/Roots: tufted, with fibrous roots
Leaves: linear, alternate, two-ranked, basally attached, 0.3-0.7 m long, 1-2 cm wide at base
Flowers: yellow, bilaterally symmetrical, bisexual, surrounded by spined bracts, along a simple spike inflorescence; villous (woolly) along the inflorescence; only one stamen
Fruits/Seeds: three-valved, dehiscent capsules with hundreds to thousands of 0.7 mm long seeds
Look-a-likes: Scheuchzeria palustris, Xyris ambigua, and Juncus spp.
Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Philydrum lanuginosum are found here.
Table last updated 3/28/2025
† Populations may not be currently present.
Ecology: Life History: growing season is June-October. Flowering (June-July) occurs for one day and the flowers are self-pollinating (Wu and Larsen 2000); seeds float and can germinate underwater with high viability (Prentis et al. 2006). Seeds did not require dormancy when germinated in a laboratory (Bridget Lassiter, North Carolina Department of Agriculture and Consumer Services, pers. comm. 2019).
Habitat: found mostly along margins in up to 0.6 m of water; common weed in rice patties in its native Southeast Asia (USDA 2016).
Tolerances: unknown
Community interactions: seed dispersal may be conducted via zoochory (USDA 2016).
Impact of Introduction: Summary of species impacts derived from literature review. Click on an icon to find out more...
Philydrum lanuginosum is reported as a weed in rice agriculture in Asia (Moody 1989, USDA 2016) and plantation crops in southern Thailand (Randall 2007). This species is considered a weed in Cambodia, Myanmar, Laos, Malaysia, Thailand, and Vietnam (NC Department of Agriculture & Consumer Services 2019). This species has also been reported to be potentially toxic to cattle (McKenzie 1997).
USDA (2016) Weed Risk Assessment of P. lanuginosum suggests that this species could affect local species diversity and may present a threat to Threatened and Endangered plant species in similar habitats.
References: (click for full references)
McKenzie, R. 1997. Australian native poisonous plants. http://anpsa.org.au/APOL7/sep97-4.html. Created on 09/01/1997. Accessed on 07/12/2019.
Moody, K. 1989. Weeds reported in rice in south and southeast Asia. International Rice Research Institute, Manila, Philippines.
NC Department of Agriculture & Consumer Services. 2019. Pest alert: wooly frogs mouth. http://www.ncagr.gov/plantindustry/plant/entomology/documents/WoolyFrogsMouthPestAlert.pdf.
Ohwi, J. 1965. Flora of Japan. National Science Museum, Tokyo, Japan.
Prentis, P.J., N.M. Meyers, and P.B. Mather. 2006. Significance of post-germination buoyancy in Helmholtzia glaberrima and Philydrum lanuginosum (Philydraceae). Australian Journal of Botany 54:11-16. http://dx.doi.org/10.1071/BT04208.
Randall, R. 2007. A global compendium of weeds. http://www.hear.org/gcw/. Created on 01/24/2007. Accessed on 07/12/2019.
Stone, B.C. 1970. The flora of Guam: A manual for the indentification of the vascular plants of the island. Micronesica 6:1-657.
USDA. 2016. Weed Risk Assessment for Philydrum lanuginosum Banks ex Gaertn. (Philydraceae) – Woolly frogs mouth. Animal and Plant Health Inspection Service, Raleigh, NC.
Wu, G., and K. Larsen. 2000. Philydraceae. Page 43 in Flora of China. Volume 24. eFloras.
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.
