Horticulturists have identified nearly 1,500 species of begonia. While these flowering plants generally thrive in warm, tropical environments, specially bred varietals can withstand cold winter temperatures. The most cold hardy begonias grow up to U.S. Department of Agriculture Plant Hardiness Zone 7, a region that often experiences freezing weather.
Semperflorens, or wax begonia, generally tolerate cold weather in U.S. Department of Agriculture Plant Hardiness zones 8 through 10, an area that subjects plants to temperatures as low as 10 degrees Fahrenheit. The Barbara Rogers begonia survives the freezing weather as far north as zone 7. This begonia grows up to 5 feet tall and bears long-lasting white flowers.
Horticulturists consider Begonia grandis the most cold hardy of its species. This tuberous begonia includes several varietals, such as Heron’s Pirouette, Sapporo and Pink Parasol. These tuberous begonias survive freezing weather up to U.S. Department of Agriculture Plant Hardiness Zone 6, which challenges most other begonia species with winter lows that reach minus 10 degrees Fahrenheit.
Cold hardy rhizomatous begonias include the Begonia emeiensis and Begonia chitoensis. Both can survive winter temperatures as low as 0 degrees Fahrenheit, typical in U.S. Department of Agriculture Plant Hardiness Zone 7. During winter, these begonias drop their leaves and may appear to rot or die. The roots do not die, however, and when warmer weather arrives they produce a new plant with showy leaves.