As we move from our cool season into the warm season, many gardeners start thinking about weather conditions, such as the dates of the last frost and freeze, and consider whether it’s safe to plant any particular plant or seed.
The average date of first freeze in East Baton Rouge Parish in the fall is Nov. 20-25, according to LSU AgCenter horticulturist Allen Owings. Average date of the last freeze is March 5-10, and the date of the possibility of a frost without a freeze is normally March 15-20.
It’s best to consider these dates and then watch the 10- and 15-day extended weather forecasts prior to planting frost-sensitive plants in late winter and early spring.
“Microclimate is significant in East Baton Rouge,” Owings says. “Spanish Town can be no frost, no freeze while fields at the Botanic Gardens at Burden on Essen Lane have frost.”
For best results, Owings recommends selecting plants recommended for U.S. Department of Agriculture hardiness zones 8 and 9 and for American Horticulture Society heat zones 8 and 9.
These hardiness zones indicate the average minimum temperature that occurs during the winter in different geographical regions.
The area north of I-12 and east of the Mississippi River generally falls in zone 8b, which has an average annual extreme minimum temperature of 15-20 degrees. The areas south of I-12 and west of the river, with the exception of New Orleans and southern Plaquemines and St. Bernard parishes, have an average annual extreme minimum temperature of 20-25 degrees.
The American Horticulture Society’s heat zones, on the other hand, are based on the average number of days per year the temperature reaches 86 degrees or higher.
Most of Louisiana, including the Greater Baton Rouge area, is in heat zone 9, which has 120-150 days of 86 degrees or higher during the calendar year.
So choosing hardy plants that can reliably survive winter cold is important to a successful landscape. Plants need to have the ability to tolerate our cold growing conditions in winter and our hot growing conditions in summer.
“As spring arrives, we need to be aware of the temperature and climate considerations that can influence our decision making in our landscapes,” Owings says.
Got a gardening question? Write to GardenNews@agcenter.lsu.edu.