Duckweed dapples the smooth water surface in a pond.
U.S. Department of Agriculture plant hardiness zone 7a endures cool winters as cold as 0 to 5 degrees Fahrenheit. Once ice melts from outdoor water gardens and water temperatures warm to at least 50 degrees, the first floating aquatic plants may be added to the pond. Does this Spark an idea?
Types and Time Frame
Hardy floating plants, those that overwinter outdoors in USDA zone 7a, tolerate colder water temperatures and may be placed in the water in late March or April. If water is too cold, the plants may remain dormant or undergo shock. Tropical plants tolerate water temperatures as low as 50 degrees but are best placed in the pond when the water is no less than 65 degrees, such as in May.
Geography
USDA zone 7a includes the cities of Reno, Oklahoma City, Memphis, Greensboro, Richmond, Annapolis, Atlantic City and most of Long Island. Latitude and elevation varies among these locations, so gardeners must definitely wait till after the last expected spring frost date in their area before releasing floating plants into the pool.
Considerations
Hardy plants like duckweed or Carolina mosquito fern may submerge themselves if put into water that's too chilly in spring. Tropical plants like water hyacinth will be killed by late frosts, and cold water will make their leaves yellow. Tropicals will sprout and green up if their roots and leaf crowns are not damaged from cold.
Tags: water temperatures, plants like, Tropical plants, USDA zone