When selecting suitable plants for their gardens, Florida homeowners need to know about conditions in their region. In Central Florida, the tri-county area of Citrus, Levy and Marion Counties is in United States Department of Agriculture (USDA) plant hardiness zone 9A with a warmer 9B area along the Gulf Coast. Average annual extreme winter temperatures in 9A are 20 to 25 degrees Fahrenheit: 5 degrees warmer in 9B.
Average annual rainfall in the western part of Central Florida is 52 to 56 inches — mostly in the summer rainy season between mid-June and mid-October. The dry season is from mid-April to early June, when supplemental irrigation may be needed in gardens. Earth’s climate is continually monitored, and data recorded so scientists can compile reports and publish maps anyone can see on the internet.
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Global standards put Central, North and West Florida in a humid subtropical climate zone. As Florida is north of the Tropic of Cancer, 23.5°N latitude, no part of Florida is within the tropics. However, the Keys and coastal South Florida benefit from the warm Gulf Stream ocean current passing close offshore, so many tropical species can grow in these warmer regions.
The islands west of Key West are in zone 11A, 45–50°F. From coastal Miami south to Key West is zone 11A with low winter temperatures between 40–45°F. The tip of peninsular South Florida is in cold zone 10B around the Everglades and along the Atlantic coast to West Palm Beach. There it is warm year-round, has no frosts and average annual extreme winter temperatures are 35–40°F. South of Lake Okeechobee and a little north on both coasts, zone 10B, 30–35°F, rarely has frosts. Zone 9B includes Tampa, Sarasota, Orlando and Cape Canaveral and has winter frosts and freezing at 25–30°F minimum winter temperatures. Tropical plants will freeze to death from 9B and northward. North and West Florida are in zone 8B except for the warmed 9A Gulf Coast and a patch of freezing 8A on the panhandle border with Georgia.
Peninsular Florida is basically a series of sand dunes built up over a former coral reef. Its central ridge of dunes became higher as the seas lowered during past ice ages. Sand dunes cover underlying rock made mostly of limestone, a sedimentary rock made from accumulations of shell, coral and algal, fecal and other debris. Limestone can form in clear, calm, warm, shallow seas. Chemically, limestone is made of calcite, a calcium carbonite mineral. When limestone contains dolomite with calcium magnesium carbonate in it, the rock is called dolomitic limestone.
Porous limestone holds water in aquifers. Limestone dissolves in acidic water. Around the world, limestone regions are called Karst topography characterized by caves, caverns, underground rivers and surface sinkholes. By choosing plants that can grow in Florida’s climate and sandy soil, any garden can prosper. Native plants, well adapted to local conditions, are perfect choices.
Plant growers propagate and raise any species that will grow easily in their zones. Some rooted cuttings are imported from Central America, where labor is cheap. Most growers use a chipped pine bark growing medium as it is lightweight and well-drained, so costs less to transport. Wholesalers re-pot small plants into bigger pots, fertilize each pot with a time-release fertilizer and irrigate daily so plants grow quickly. Landscape professionals buy plants for their customers from wholesalers. Big box nursery outlets order truckloads directly from growers.
As retail customers, homeowners need to read plant tags, determine the species’ preferred growing conditions and research each plant characteristics and needs before they decide what to buy. Tropical species may thrive in South Florida and the Keys but will need to be protected from cold winter winds and regular freezes in our zone 9A. Most plants will need irrigation at least once a week in our dry winter season. Covering frost-tender plants is a major chore.
For example, in zone 9B, native Firebush, Hamelia patens, is a 10 foot tall evergreen flowering shrub that can be pruned into a compact dense bush. In zone 9A, Firebush will get frost bitten and may die right to the ground. New stems and leaves will likely sprout from the roots in mid-spring.
Other plants, including some tropical gingers, die back in late autumn and go dormant for the winter. Bear in mind that many plants are deciduous and lose their leaves for winter. Examples are trees like maple, sycamore, birch and elm; shrubs like beautyberry, crapemyrtle, pawpaw and hibiscus; as well as perennials like goldenrod, liatris and grapevines. Warm season turfgrasses also go dormant in the cool winter in Central Florida.
Jane Weber is a professional gardener and consultant. Semi-retired, she grows thousands of native plants. Contact her at [email protected] or phone 352-249-6899.