Habit: Perennial, floating and emergent, herbaceous forb

Stem/roots: non-flowering, sprawling stems float along the water surface with roots at the stem nodes; upright stems freely branching and flowering; pubescent

Leaves: alternating leaves on floating stems are spatulate (spoon-shaped), petiolate (leaf stems), and have rounded apices; alternating leaves on upright stems are lanceolate (lance-shaped), mostly sessile, and have acute apices; pubescent

Flowers: solitary flowers at leaf axils of upright stems; pedicels 1-5 cm, usually confused with floral tubes; a pair of small bractlets indicate the separation of the pedicel and floral tube; pedicel and floral tube pubescent; calyx of 5, sometimes 6, acute sepals, 10-12 mm, pubescent on the outside; corolla of 5, sometimes 6, bright yellow, rounded petals, 1-2 cm long and wide; stamens 8-12, twice the amount of sepals/petals

Fruits: fruit a pubescent, cylindric capsule 1-2.5 cm long, 3-4 mm wide

Look-alikes: Many Ludwigia species have similar leaves and flowers, but those two organs are key to determining identity. The alternate leave arrangement, the 8-12 stamens, and the 5-6 petals differentiate to about four species. The Ludwigia uruguayensis species complex includes L. grandiflora and L. hexapetala. Leaves on upright stems will be mostly lanceolate (widest portion of the leaf in the leaf center) on L. grandiflora and mostly oblanceolate (widest portion of the leaf in the top half of the leaf) on L. hexapetala, and stem nodes are swollen along the lower portion of upright stems on L. hexapetala (Colette Jacono, Univ. of Florida, pers. comm. 2017). Upright stems of L. grandiflora have pubescent stems, leaves, and floral tubes, distinguishing them from L. peploides, which are mostly glabrous (hairless) and lack upright stems. Floral tubes/capsules of L. grandiflora are narrower and longer than those of L. peruviana, which have stout and pyramidal floral tubes/capsules. The native L. leptocarpa has smaller petals (<1 cm) than those of L. grandiflora (>1 cm), usually the same length as the sepals.

Life history: self-compatible flowers will self-fertilize; most reproduction is through vegatative fragmentation of stems; flowers from April to September; seeds remain embedded in woody capsules (Okada et al. 2009; Les 2018)

Habitat: marshes, swamps, ponds, lakes, ditches, canals, and wet disturbed areas (Godfrey and Wooten 1981; Les 2018)

Tolerances: fresh to brackish (0-3.5 ppt salinity); pH 6.1-7.3; depths to 2.4 m; elevations to 102 m; poorly drained muck and sandy clay; fire-, flood-, graze-, and mow- tolerant over short periods (Les 2018)

Community interactions: pollinated by generalists (bees, butterflies, and flowerflies); waterfowl consume the seeds of L. grandiflora; Lysathia ludoviciana leaf beetles consume the foliage of L. grandiflora (Les 2018)

Summary of species impacts derived from literature review. Click on an icon to find out more...

Ecological	Economic	Human Health	Other

Ecological impacts

Ludwigia grandiflora creates large homogenous mats that outcompete other organisms for essential resources, such as light, nutrients, and open water habitat for waterfowl (Nehring and Kolthoff 2011, Stiers et al. 2011, Grewell et al. 2016). Invertebrate richness and abundance declined in ponds with high abundance of L. grandiflora due to increased decomposition and decreased dissolved oxygen (Stiers et al. 2011). However, pollinator densities increased in communities with L. grandiflora, but native plant species richness, especially submerged plants, declined due to decreased sunlight availability and oxygen exchange (Stiers et al. 2011, Stiers et al. 2014). Through allelopathic chemicals, L. grandiflora inhibited Lactuca sativa and Nasturtium officinale germination when grown in mixtures (Dandelot et al. 2008).