Long Beach Primrose-willow

Ludwigia brevipes and Ludwigia arcuata are sold as each other often enough that Flowgrow warns about it. Submersed, the two narrow-leaved stems are easy to confuse. The reliable separation happens above the waterline, in flower: brevipes has smaller, narrower petals and hairless stems, while arcuata has relatively large petals and stems with a light covering of hairs. This entry follows Flowgrow's brevipes page.

The plant is North American. It grows in boggy ground along the Atlantic coastal plain of the southeastern United States, in Virginia, the Carolinas and northwestern Florida, and Flowgrow gives it the common name Long Beach primrose-willow.

Light does most of the work here. The page names sufficient light, 0.5 watts per litre or above, as the most important factor in submersed culture, and treats fertiliser as the supporting act: micro and macronutrients help, particularly if you inject CO2. That conditional is why this entry now sits at optional rather than required. Colour follows the nutrient balance, with low nitrate against relatively high phosphate turning the shoot tips reddish to orange.

The published conditions are 22 to 26 °C and pH 4.5 to 7, with carbonate hardness from 2 to 10 dKH, medium to high light, fast growth and medium difficulty. Trimming and propagation are the same job: cut off a shoot tip or a lateral shoot and replant it, and the cut plant answers with more laterals and a bushier habit. Flowgrow suggests planting it in groups in the midground with Micranthemum umbrosum or Bacopa australis for contrast. It publishes no height figure, so the 25 cm here is editorial.