South-Florida-Plant-Guide's plant zone map is a good indicator of what winter temperatures you can expect where YOU live...and what plants will work for you.
Zone 9A - Low temperatures of 20-25 degrees Fahrenheit
Zone 9B - 25-30 degrees
Zone 10A - 30-35 degrees
Zone 10B - 35-40 degrees
Sometimes knowing exactly which zone you're in - plant zones can actually shift a bit from year to year - AND which plants to buy can be confusing.
You can actually be in one zone and your friends or family living a few miles away can be in another.
If you live in an area that borders two planting zones, consult a local plant nursery you trust. Tell them where your home is located and they can recommend plants that will do well there.
Not all maps are alike...this one is MY version, based on many things.
I've lived here in South Florida for over 20 years and have experienced real-life temperature variations...not only in my own home landscape but also in the plant nursery business.
Low temperatures can damage nursery stock plants in pots more than established ones in the ground at people's homes. It takes careful planning and a lot of work to bring thousands of plants through any given winter without cold damage and inventory loss.
And, in the nursery business, there's almost daily communication between nurseries regarding winter temperatures. We purchase stock and special-order plants from each other year round, and because cold is a plant nursery's enemy, we have a working knowledge of what winter temperatures are on a day-to-day basis around the southern half of Florida.
Planting zones can actually flip flop around depending on the weather.
For instance, I live in western Manatee County on the Gulf Coast, and for most of the past 2 decades have been situated in Zone 10A with only occasional dips into Zone 9B temps.
Then along came the winter of 2009-2010. Record-breaking cold - weeks at a stretch in the mid 20's at night - that catapulted our area into Zone 9B to 9A.
There was a tremendous amount of cold damage to plants all over southern Florida that year. Trend or fluke? No one really knows...and Mother Nature's not talking.
Mapping temperate zones is not an exact science, and you'll find this plant zone map differs from the USDA version and others.
But this plant zone map is based on long-term real experience of living in South Florida. That's about as accurate as you can get with predicting weather!
If a super-cold winter comes along, expect some damage even on cold hardy plants. Check out the Cold Protection page for more info on how to prevent and deal with damage from cold.
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