St. Johns County, in Florida, sits in USDA hardiness zone 9b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
These conditions suit mango, tomato, orange, and sweet potato — a starting list any specific site will trim or extend with its own soil, sun, and drainage.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring
St. Johns County holds more than one microclimate.
Soils and elevations shift across St. Johns County, so your frost dates and drainage aren't the county average. Enter your address and we'll score 1,112 plants against your land's actual soil, sun, and frost.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Quick Facts
USDA Zones
9b
Last Frost (state avg.)
Jan 1 - Mar 15
First Frost (state avg.)
Nov 15 - never (south FL)
County Area
384K acres
Hardiness Zone Range
Growing Season
Zone maps are averages across St. Johns County. Your yard's slope, trees, and frost pockets shift what actually grows — see your land's exact reading.
Soil in St. Johns County
Across St. Johns County, the ground is predominantly Spodosols, where Riviera, Myakka, and Pomona are the most extensive named soil series. The soil is generally poorly drained with a fine sand surface. Topsoil pH runs about 5.0–5.6, strongly acidic. Rainfall drains through hydrologic group A/D soils.
Soil order
Spodosols
Drainage
Poorly drained
Hydric soils
48%
Soil still varies lot by lot — soil types explained.
What Grows in St. Johns County
Plants matched to St. Johns County's USDA zones 9b — each links to its full growing profile.
Growing Challenges in Florida
What an experienced grower plans around here — each one has a move.
Sandy soils drain too fast and hold few nutrients — frequent fertilization needed
Build organic matter relentlessly — compost and cover crops turn sand into soil that holds both water and food.
Humidity drives fungal diseases (powdery mildew, black spot, rust)
Space plants for airflow, water at the base in the morning, and choose resistant varieties — your extension office lists the proven ones.
Hurricane season (June-November) can destroy plantings
Favor wind-tough perennials, stake young trees properly, and keep fall crops in containers you can move ahead of a storm.
Nematodes are a serious pest in sandy FL soils
Summer solarization and crop-family rotation knock nematodes back — your extension office can confirm the species from a soil sample.
For cultivar selection, pest pressure, and planting-time guidance specific to Florida, the UF/IFAS Extension is the authoritative local source.
Safe to Grow Here?
What the federal record shows across St. Johns County — and how to grow with it.
We checked the federal record across St. Johns County — 580 documented sites across 6 of the 9 source types we track.
The most significant on record: 4 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
St. Johns County carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds with clean imported soil grow well almost anywhere in the meantime.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Environmental Intelligence
Understanding what's nearby helps you make informed decisions about where and how to grow.
Sources Checked
across St. Johns County
Severity Distribution
across St. Johns County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around St. Johns County, PFAS runs higher than the national average — 8 sites nearby. That's not a problem with your land — it's information about it.
PFAS: PFAS (per- and polyfluoroalkyl substances) are called "forever chemicals" because they do not biodegrade.
Test irrigation water source — this is the primary pathway for PFAS to reach garden crops.
Check your specific parcel in St. Johns County
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,112 plant recommendations.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources analyzed in seconds
Your Specific Parcel Matters
St. Johns County Average
- ●USDA Zones 9b
- ●Generic soil type for the area
- ●State-average frost dates
YOUR Parcel
- ✓Your exact hardiness zone
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in St. Johns County
Pull a site-specific report for your exact address in St. Johns County, Florida — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources analyzed in seconds
Key Growing Facts for St. Johns County, Florida
- USDA Hardiness Zones: 9b (USDA PHZM 2023)
- Last Spring Frost (state avg.): Jan 1 - Mar 15 (NOAA 30-Year Climate Normals)
- First Fall Frost (state avg.): Nov 15 - never (south FL) (NOAA 30-Year Climate Normals)
- County Land Area: 384K acres (US Census TIGER 2025)
Zone data: USDA ARS Plant Hardiness Zone Map 2023. Climate data: NOAA NCEI. County boundaries: US Census TIGER/Line 2025.
Frost dates here are the St. Johns County average. Low spots and tree cover move them by days on any one yard — see your exact frost windows.
Frequently Asked Questions
What hardiness zone is St. Johns County, Florida?
St. Johns County sits in USDA hardiness zone 9b, per the USDA Plant Hardiness Zone Map 2023. Zones reflect average annual extreme minimum temperatures from 1991–2020 weather data.
When does frost risk typically end in St. Johns County?
St. Johns County follows Florida's statewide frost window: last spring frost around Jan 1 - Mar 15 and first fall frost around Nov 15 - never (south FL), per NOAA 30-year climate normals (1991–2020). Frost dates shift with elevation and local microclimate, so watch your own site's cold pockets.
What vegetables grow in St. Johns County?
St. Johns County's zone 9b supports a wide range — strong performers include Mango, Tomato, Orange, Sweet Potato, and Banana. What actually takes on any one site comes down to its soil, sun, and drainage, and we score each plant against the real conditions at your address.
Which hardiness zone is St. Johns County, really?
Officially, St. Johns County sits in USDA zone 9b (USDA PHZM 2023) — but a zone is a 30-year average of winter's coldest night across an area, and it can't see any one yard. A south-facing slope, a tree line, or a low frost pocket can shift a single site by half a zone either way, which is why neighboring gardeners often quote different numbers. We read the conditions at your exact address — soil, sun, slope, and frost — and score 1,112 plants against what's actually there.
Is the soil safe to grow vegetables in St. Johns County?
The federal record around St. Johns County runs heavier than most — 580 documented sites — so test the soil before planting food in the ground, and raised beds with clean imported soil grow well in the meantime. Even here, proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what's recorded and where.
Just moved to St. Johns County — what should I know before planting?
Start with three facts. St. Johns County sits in USDA zone 9b, which sets what survives winter; the statewide frost window runs about Jan 1 - Mar 15 to Nov 15 - never (south FL) (NOAA 30-year climate normals); and 580 documented sites sit on the federal record here, so a soil test before food beds is the smart first step. From there, matching plants to your actual soil and sun is the fun part.
Everything on this page is a St. Johns County average. Your yard writes its own version — we read soil, sun, drainage, and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads Florida's frost window, season length, and soil profile against the plant's real requirements.