Water hyacinth (Eichhornia crassipes) are known for their lavender-blue flowers and round floating leaves.  They grow quickly in warm water.  They are a welcome addition to your water garden for their ability to filter out unwanted nutrients.  The flowers only last a day or two but are enjoyable and create a nice feature in you pond.  A great floating plant for creating shade and a hiding place for your fish.  They require water temperatures to be 65 degrees.  If you put them in too early in the spring,  cooler air and cooler water temperatures can cause them to yellow or get black spots on their leaves and possibly die back.

Buy water hyacinth-floating water plants here.