Photos for outreach. South American spongeplant, Limnobium laevigatum, in California, Prepared by Patrick Akers Calif. Dept. of Food & Agric. The California Dept. of Food & Agriculture provides these photographs for those who want to learn about spongeplant and pass on the information. Photos may be used freely for non-commercial purposes. Please acknowledge the Department as the source.

ID: young, uncrowded spongeplant Note white female flower and daughter plant on stolon (runner) coming off larger plant Uncrowded spongeplant has leaves that lie flat on the water, the leaves are thick near the stem and curve and taper towards the tip (keeled shape), and the leaf stem is shorter than or about the same length as the leaf blade.

ID: young, uncrowded spongeplant Note small daughter plant (on left) at end of runner (stolon) coming from larger parent plant. Spongeplant increases rapidly this way (vegetative reproduction), like water hyacinth does. It also reproduces heavily from seed, while hyacinth seedlings are usually very uncommon.

ID: young, uncrowded spongeplant Leaf folded in halfNote seed pod on right

ID: young, uncrowded spongeplant

ID: crowded, upright spongeplant Crowded spongeplant has leaves that are held upright, the leaves are not heavily keeled, and the leaf stem is distinctly longer than the leaf blade, sometimes as much as five times longer. In this condition spongeplant looks very much like water hyacinth, except that it typically gets only 8 to 14 inches tall.

ID: crowded, upright spongeplant

Crowded spongeplant on left, uncrowded water hyacinth on right

ID: crowded vs uncrowded Uncrowded spongeplant has leaves that lie flat on the water, the leaves are thick near the stem and curve and taper towards the tip (keeled shape), and the leaf stem is shorter than or about the same length as the leaf blade. Crowded spongeplant has leaves that are held upright, the leaves are not heavily keeled, and the leaf stem is distinctly longer than the leaf blade, sometimes as much as five times longer. In this condition spongeplant looks very much like water hyacinth, except that it typically gets only 8 to 14 inches tall.

ID: crowded vs uncrowded Grading from crowded on left to uncrowded on right

ID: spongeplant vs water hyacinth Crowded spongeplant, lower, vs crowded hyacinth, upper Crowded spongeplant, left, vs uncrowded hyacinth, right

ID: spongeplant vs water hyacinth Spongeplant leaves in red circle. Crowded spongeplant vs uncrowded hyacinth.

ID: spongeplant vs water hyacinth Uncrowded spongeplant mixed with uncrowded hyacinth

Spread in California Official state records of spongeplant locations in California. The first records of spongeplant were in 2003, in Arcata and Redding. No more spongeplant appeared until the summer of 2007, when plants were reported in the San Joaquin River in Fresno. In late December, 2007, it was found a few miles from Antioch in a patch at the western edge of the Sacramento Delta. That patch seemed to disappear after a major winter storm occurred a few days later. In February, 2008, plants were found in a canal system off the Kings River east of Fresno. In summer, 2008, it appeared in canals in western Fresno County between Mendota and Dos Palos. In 2009 and 2010, it was again found in the Delta. The Sacramento city location was in a small drain and has been eradicated.

Impacts and locations in California Redding pond, before treatment, June Spongeplant choked out water primrose and parrotsfeather in the pond. Grass beginning to grow on the mat is visible about 1/3 down from top of photo. Quadrat 0.5m on a side. Roughly 2000 to 2500 plants per square meter. Many times higher than water hyacinth.

Above: Kings river infestation east of Fresno; source pond and infested canal Above: canal after cleaning Note: the “Kings River infestation” is not in the river but in some small canals that are fed by the river. Impacts and locations in California

San Joaquin River near Fresno, patches along main channel and mat forming in back channel. Impacts and locations in California

The Main Canal in western Merced and Stanislaus Co., near the end point of the 76- mile canal. Photos are from late September, The canal company reports they did not notice any spongeplant in this area as late as July. Impacts and locations in California

Cleaning the Main Canal during October, and the condition as of late October, Impacts and locations in California

Above: Sacramento-San Joaquin Delta. Left, spreading patch; right, more mature mat. Impacts and locations in California

Above: Sacramento-San Joaquin Delta. Impacts and locations in California

Management: Treatment works well if infestation is caught early A canal in western Fresno county, before, during, and after treatment. Plants did not come back at this location. In locations where the plants have had time to establish a seed bank, they quickly return.

Reasons for impact and spread: 1. Heavy seed production Female flowers and seed pods in red ellipses. Right, a seed pod split open. Redding pond, late spring 2006

Reasons for impact and spread: 2. Small, abundant seedlings Seedlings in red ellipses. The other small plants are duckweed.

Seedlings emerging in the source pond in the Kings River canals infestation. Photos taken Oct This pond has been kept clean of mature plants since early spring Originally, it was heavily infested. Reasons for impact and spread: 3. Seeds survive at least 3 years

Thanks for your Time and Interest!