Just the few granules of zero phosphorous spring time fertilizer that the crew put down on my lawn that hit the pond will set off a spring time bloom for me. I'm sure if we got a rain soon after the fertilizer application that some run off took more fertilizer into the pond as well. My bloom lasted about 10 days last spring and then it seemed like there may have been a mid to late summer bloom again, but again, i couldnt' rule out a correlation with the mid summer fertilizer application as well to the lawn.
