I have some plants in my tank that I found in a stream and mine seemed to grow very quickly too. I think one of the plants that I have is the same thing as your "ludwigia".
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5 gallon Hex planted - Bee shrimp, algae eating shrimp, oto, snails
10 gallon planted - platy, white clouds + baby, oto, cories
~1g bowl - duckweed, male betta |