This is a gorgeous time of year in SE Louisiana, and the azaleas are blooming vigorously. By my memory, this azalea display in 2021 is much better than last year’s. To bloom their best, azaleas typically need 4-8 weeks of temperatures below 50 degrees Fahrenheit in the preceding winter. So, I wondered whether a mild winter in 2019-20 might have been responsible for the underwhelming azalea blooms in 2020.
To investigate whether there were insufficient chilly days for azaleas in the winter of 2019-20, I downloaded local temperature data for the last two years (available from NOAA). The data was from a nearby small airport and consisted of daily min and max temperatures. These two values were averaged to estimate an average temperature for each day. In the chart below these average temperatures are plotted from mid-June 2020 to mid-March 2021.
Tallying sub-50 degF days reveals there were 20 in the winter of 2019-20 (slightly less than 3 weeks) and 38 in the winter of 2020-21 (more than 5 weeks). Recalling that 4-8 weeks of chilling are needed for optimum azalea blooming, it does seem that a mild winter may have led to a disappointing show of azaleas in 2020.