Water Hyacinths are nearly care-free water plants with pretty, lilac blue flowers, but watch out -- these can be real pests in warm, open water. In Florida they have proliferated so rapidly they have blocked rivers and other waterways. Thin year-round. Needs calm water, preferably more than 1 foot deep. Winter indoors in cold climates.
Floating on air-filled leaf stalks, this prolific bloomer thrives in an open, sunny spot but can be invasive if water is too warm.