I'm not sure. I don't order new each year but they have gotten wimpier each year. I remember when over half my pond was covered with lily pads. I would think that would cut down on algae as it cuts down on sun hitting the water. I use fertilizer spikes so I don't have to crawl into the pond once a month. Also have tried growing them in mud, gravel, kitty litter etc as I saw those recommended here. I returned to mud last year. They don't do very well. Maybe one or two at a time and always the same ones. I order the hardy varieties from TWL.
