Generally — Most Areas
delphinium (zones 3-7) suits most of Tennessee (6a-8a) — zones 6-7 are in range, and the rest of the state is the exception.
Your yard isn't the whole zone.
Tennessee spans zones 6a-8a, but your yard has its own microclimate — slope, trees, and low spots shift frost and sun across a single parcel. Enter your address and we'll score delphinium against your land's actual soil, sun, and frost.
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Zone Comparison
Delphinium Needs
- USDA Zones: 3-7
- Mature size: 5 ft tall
- Picking window: ~30 days of harvest
- Drought tolerance: Low
Tennessee Has
- USDA Zones: 6a-8a
- Last Hard Freeze (28°F): Mar 21 - Mar 29
- First Hard Freeze (28°F): Nov 5 - Nov 12
- Annual Rainfall: 45-55 inches
- Common Soils: Silt loam, Clay loam, Limestone-derived
Plant Zone Range (zones 3-7)
Plant data: USDA PLANTS Database / Growable Ground plant catalog. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Delphinium in Tennessee
The frost window
Across Tennessee, the last spring hard freeze (28°F) clears between Mar 21 and Mar 29, and the first fall hard freeze lands between Nov 5 and Nov 12 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 221-day window you can count on — up to 236 days on a mild site in a kind year. That marks the hard freeze, not the last light frost, so tender transplants usually wait another 2-3 weeks.
When to start the seed
Those dates are when delphinium goes out, not when it starts. It is sown under cover about 8 weeks ahead, so counting back from Tennessee's late-side last freeze of Mar 29 is what fixes your sowing date — and a yard that clears frost earlier than the state's late date starts earlier still.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: USDA PLANTS Database. Your site's own frost dates can run earlier or later than the state range — a parcel report pins them down.
Delphinium in Tennessee — Quick Answer
- Verdict: Generally — Most Areas
- Plant Zones: 3-7 (USDA PLANTS Database)
- State Zones: 6a-8a (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Mar 21 - Mar 29 to Nov 5 - Nov 12 (NOAA Regional Climate Centers ACIS, 1991-2020)
What Else to Consider for Delphinium in Tennessee
Zone compatibility tells you about winter cold survival — but Tennessee growers also need to think about:
Heavy clay soils in the Nashville Basin
High humidity promotes disease in summer
Variable spring weather with late frost risk
What to actually do about these — and the constraints that apply to every Tennessee grower, not just delphinium — is covered on the Tennessee growing guide.
Where in Tennessee Delphinium Is Zone-Hardy
Delphinium is rated for USDA zones 3–7. 21 of Tennessee’s 95 counties fall inside that band. The coldest that does is Carter County at zone 7a. 74 counties sit above its zone 7 ceiling, where the limit is too little winter chill rather than too much cold. Where you are in Tennessee decides this one.
Across those 95 counties Tennessee’s winter-low ladder runs from zone 7a in Carter County to zone 8a in Tipton County — 1 USDA zone of spread, which is 10°F between the two counties’ average coldest night of the year. That is why a statewide hardiness answer is where you start and not where you finish.
The planting window moves with it. Johnson County holds its last hard freeze (28°F) until about Apr 14, while Shelby County is clear by Mar 4 — 41 days apart. Set delphinium out on your county’s date, not the state’s.
County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. County last-freeze dates: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F killing freeze — earlier than the folk 32°F "last frost". Delphinium’s zone 3–7 band: USDA PLANTS / Growable Ground plant database. A parcel report resolves your address’s own zone and frost dates rather than its county’s.
Where in Tennessee Fits Best
Even within Tennessee's zones 6a-8a, county microclimates differ enough to change what thrives. These counties carry the closest zone match for delphinium (USDA PHZM 2023):
Pollinator + Wildlife Value
Delphinium draws native bees, butterflies, and hummingbirds (moderate value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, delphinium can only work that bloom inside Tennessee's frost window — roughly 230 days, opening after the last 28°F freeze (Mar 21 - Mar 29) and closing at the first (Nov 5 - Nov 12), per NOAA Regional Climate Centers ACIS, 1991-2020.
Tennessee Cooperative Extension
For Tennessee-specific cultivar recommendations, planting calendars, and pest pressure for delphinium, the canonical source is UT Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Delphinium native to Tennessee?
No — the USDA PLANTS Database lists Delphinium as introduced rather than native in the Lower 48, so it is not part of Tennessee's native flora. It grows here as a garden plant; pairing it with a few Tennessee natives keeps local pollinators fed too.
Looking for plants that belong here? The Tennessee growing guide lists USDA-documented natives for the state.
Native-range data: USDA PLANTS Database state-distribution records, accessed 2026-07-01.
Common Questions About Growing Delphinium in Tennessee
When can I plant Delphinium in Tennessee?
Tennessee's last spring hard freeze (28°F) clears between Mar 21 and Mar 29, and the first fall hard freeze lands between Nov 5 and Nov 12 (NOAA Regional Climate Centers ACIS, 1991-2020). Time outdoor planting to after the last hard freeze for your specific site — a further two to three weeks for anything tender — and count back from those dates for transplant scheduling.
What hardiness zone is Delphinium grown in across Tennessee?
Tennessee spans USDA hardiness zones 6a-8a (USDA ARS PHZM 2023). Delphinium carries a range of zones 3-7, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Tennessee site have?
A typical Tennessee site sees ~230 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Delphinium should be matched against that window, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Delphinium native to Tennessee?
No — the USDA PLANTS Database lists Delphinium as introduced rather than native in the Lower 48, so it is not part of Tennessee's native flora. It grows here as a garden plant; pairing it with a few Tennessee natives keeps local pollinators fed too.
Will Delphinium actually grow on my specific land in Tennessee?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores delphinium against your address's exact soil pH, drainage, sun, and frost-date data drawn from USDA SSURGO, NOAA, and PRISM — not state averages.
Check your specific parcel in Tennessee
State-level data is a sketch. Your Growable Ground report scores delphinium against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Tennessee delphinium averages can't show:
We read public map data around Tennessee — soil, climate, flood, and parcel records. How we handle your address.
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Growing guides for delphinium
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