Phyllanthus urinaria L.; Chamberbitter

California Pest Rating
Phyllanthus urinaria L.; Chamberbitter
Euphorbiaceae; Malpighiales
Pest Rating: C | Proposed Seed Rating: R

Initiating Event:

The species was given a temporary Q rating in 2014.

History & Status:

Chamberbitter is an herbaceous, annual herb that can grow 20-70 cm in height. The leaves are elliptic and borne distichously along the stem. They are superficially similar to those of sensitive plant (Mimosa pudica), but in fact sensitive plant has compound leaves with elliptic leaflets. The small flowers are sessile under the leaf axils and quickly give rise to six-lobed, pumpkin-shaped fruits that dehisce explosively releasing 6 seeds. Chamberbitter seems not to be native to the United States, but it is a widely distributed tropical weed. It is weedy species nurseries, gardens and lawns in tropical areas. It is a pest of rice in Southeast Asia.

Official Control: Chamberbitter has been a “Q” listed weed in California since late 2014.

California DistributionChamberbitter currently is not known from California.

California Interceptions: Chamberbitter has been detected in nursery stock entering California from Florida.

United States:  Chamberbitter is widespread in the Southern United States. It is listed as a noxious weed in Alabama.

International: Chamberbitter is reported as naturalized and as an environmental and agricultural weed in much of the tropics.

The risk Chamberbitter would pose to California is evaluated below.

 Consequences of Introduction: 

1) Climate/Host Interaction: It is an invasive species of disturbed areas, nurseries, lawns and wet fields in the tropics and subtropics. Although it may spread in agricultural situations with adequate water, chamberbitter is unlikely to be suited to escape widely in the environment, except in warmer areas that have abundant water in the late spring and summer. This might apply in nurseries in Southern California, as well as in some rice fields. It scores as Medium (2) in this category.

Evaluate if the pest would have suitable hosts and climate to establish in California.  Score:

-Low (1) Not likely to establish in California; or likely to establish in very limited areas.
-Medium (2) may be able to establish in a larger but limited part of California.
-High (3) likely to establish a widespread distribution in California.

2) Host Range: Risk is High (3) as weeds do not require any one host, but grow wherever ecological conditions are favorable.

Evaluate the host range of the pest. Score:

-Low (1) has a very limited host range.
-Medium (2) has a moderate host range.
High (3) has a wide host range.

3) Pest Dispersal Potential: Chamberbitter is a prolific seed producer that disperses its seeds via explosive fruits. The seeds can remain dormant for an extended period of time. They germinate during the wet, warm conditions and the seedlings mature quickly (within 2 weeks in some cases). Seed requires light to germinate. A germination rate of up to 80% was observed at temperatures of 25–35°C, but germination was poor at 20°C or 40°C. Germination of seed is also poor under moisture stress conditions. Chamberbitter receives a High (3) in this category.

Evaluate the natural and artificial dispersal potential of the pest. Score:

-Low (1) does not have high reproductive or dispersal potential.
-Medium (2) has either high reproductive or dispersal potential.
High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Chamberbitter is a weed in some agricultural situations. Its worst effects are as a lawn weed that is difficult to eradicate. Chamberbitter receives a Low (1) in this category.

Evaluate the economic impact of the pest to California using the criteria below. Score:

A.  The pest could lower crop yield

B.  The pest could lower crop value (includes increasing crop production costs)

C.  The pest could trigger the loss of markets (includes quarantines by other states or countries)

D.  The pest could negatively change normal production cultural practices

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Low (1) causes 0 or 1 of these impacts
-Medium (2) causes 2 of these impacts
-High (3) causes 3 or more of these impacts

5) Environmental Impact: The plant has not yet spread in California. If it does spread, Chamberbitter might trigger new treatments by nursery and turf farm managers. Chamberbitter receives a Low (1) in this category.

Evaluate the environmental impact of the pest on California using the criteria below.

A.  The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B.  The pest could directly affect threatened or endangered species.

C.  The pest could impact threatened or endangered species by disrupting critical habitats.

D.  The pest could trigger additional official or private treatment programs.

E.  Significantly impacting cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact.

Low (1) causes none of the above to occur
-Medium (2) causes one of the above to occur
-High (3) causes two or more of the above to occur

Consequences of Introduction to California for Chamberbitter: Medium (10)

Add up the total score and include it here.

-Low = 5-8 points
Medium = 9-12 points
-High = 13-15 points

6) Post Entry Distribution and Survey Information: Chamberbitter has not been found established in California. Its range at this time is limited. It receives a (0) in this category.

Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Not established (0) Pest never detected in California, or known only from incursions.
Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

The final score is the consequences of introduction score minus the post entry distribution and survey information score: Medium (10)


This plant is not widely adapted to the dry environments of California. Nevertheless, locally in warmer areas with irrigation, it could invade and prove troublesome. It is an especially invasive pests of nurseries and well watered lawns.

Conclusion and Rating Justification:

Chamberbitter is a potential weed of nurseries, turf farms and watered gardens in southern California. It may invade irrigated crops such as rice and cotton in warm areas as well, although this is less likely given the management regime in CA rice fields. Because of its real but restricted potential to invade California, chamberbitter deserves for a C pest rating.


Baldwin, B. G., D. H. Goldman, D. J. Keil, R. Patterson, T. J. Rosatti, and D. H. Wilken, editors. 2012. The Jepson manual: vascular plants of California, second edition. University of California Press, Berkeley.

Consortium of California Herbaria:

Flora of North America Editorial Committee, eds.  1993+.  Flora of North America North of Mexico.  16+ vols.  New York and Oxford.

Weaver, R. 2010. Phyllanthus urinaria L., the chamber bitter or gripe weed. Accessed 5/23/2015:

USDA Plant Profile: Phyllanthus urinaria. Accessed May 16, 2015:

Responsible Party:

Dean G. Kelch, Primary Botanist; California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 654-0312;[@]

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Pest Rating: C | Proposed Seed Rating: R

Posted by ls