It's been another warm winter here in My Florida Backyard, and coupled with last year's complete lack of a hard freeze, some of our plants are getting a very early start. We were astonished this year to find our hippeastrum already pushing up shoots in mid-January, at least 3 weeks earlier even than last year, and more than six weeks ahead of the extremely cold winter of 2010. There's no doubt that, even in Florida, changes in average temperatures can have a real impact on plants and animals.
In the mid-1800s, Henry David Thoreau began keeping a very detailed journal documenting the first flowering dates of plants in New England. Scientists recently compared Thoreau's flowering dates to those from recent years, and discovered that, on average, plants are blooming about 11 days earlier than they did 150 years ago. In that same time, average temperatures have climbed, and scientist have worked out that flowers are blooming "up to 4.1 days earlier for every 1 degree Celsius rise in average spring temperatures, which translates to 2.3 days for every 1 degree Fahrenheit" (via National Geographic).
USDA released a new Plant Hardiness Zone Map, reflecting a shift to warmer average temperatures since the last map issued in 1990. (My Florida Backyard shifted from 9A to 9B, although our urban environment means reflected heat that really puts us in zone 10A.) This winter seems to be keeping line with those changes, with no hard freezes in the area so far, and none in the forecast despite some chilly mornings in the 40s. Other plants and trees are blooming early, with redbuds and toadflax already putting on a good show in many areas, and willow trees leafing out even in cooler inland areas.
Regardless of your belief in the impact humans are having on our climate, there's no doubt that it's changing, and at a very fast rate. Gardeners in all climates will have many changes to adjust to, and many surprises in store, in the years to come. What's blooming early by you this year? I'd love to hear some other examples of how frost-free winters are affecting Central Florida gardeners.