To apply phosphorus any time of year you must have a soil test documenting a deficiency and also have sent this information to the Pinellas County Watershed Division, Attention: Division Director, 300 South Garden Avenue, Clearwater, FL 33756 prior to the application of phosphorus.
For more information see the Pinellas County Watershed Division website
Remember June 1 Fertilizer Ban
May 31 is the last date that you can apply nitrogen or phosphorus fertilizers in Pinellas County. October 1 these fertilizers can be resumed.