South Florida's plant hardiness zones have changed
Add Axios as your preferred source to
see more of our stories on Google.
Warming temperatures are changing where and when different plant varieties can grow most successfully, as reflected in a new U.S. Department of Agriculture (USDA) map released this month, Axios' Jacque Schrag reports.
What's happening: The Plant Hardiness Zone Map is a kind of bible for farmers and gardeners, helping them understand which plants can thrive in their area and when to plant them. The map has been updated for the first time since 2012.
- The map divides the U.S. into 13 zones, each representing a range of 10 degrees Fahrenheit. Each zone is divided further into two 5-degree half zones.
- The new map shifts about half of the country to the next warmer half zone, TCPalm explains. Those parts of the country warmed 0 to 5 degrees Fahrenheit.
Details: David Whitwam with Whitwam Organics told Tampa's Fox 13 that the map is based on data measuring an area's coldest temperatures, not its hottest ones.
- The new zones are based on the average annual extreme minimum winter temperature from 1991–2020.
- The previous map, released in 2012, was based on 1976–2005 data.
- "The annual extreme minimum temperature represents the coldest night of the year, which can be highly variable from year to year, depending on local weather patterns," per the USDA.
Zoom in: The new map puts South Florida in hotter zones.
- An online tool allows users to check a zone by ZIP code.
What they're saying: Most of Miami-Dade and Broward Counties formerly fell into Zones 10A and 10B. Edible South Florida editor Gretchen Schmidt tells Axios, "Now we are 11A along the coast and 10B inland, where many of the commercial growers' crops are located."
- Growers are watching to see whether and how crop viability changes. For example, breadfruit typically only fruits in the Lower Keys and can't survive a cold snap further north, Schmidt says.
Yes, but: Some changes in the map are the result of more advanced mapping methods and data collection.
- Many factors influence whether a given plant grows successfully or not, including light, soil moisture, humidity and exposure to the elements.
- The map reflects that some areas were relabeled as colder zones.