Looks like an Aponogeton crispus, had quite a few of those in my low tech setup and like you have found out they constantly flowered. I personally removed the flowers most of the time, its up to you though. You fertilize the flower by brushing it with a small paint brush or by dipping it under water to release all the pollen and eventually it will produce large seeds which will fall off. You can then plant the seeds in the gravel , I grew a couple by doing this before they grew too big for my tank and give them to my sister.