Delphinium is grown for its blooms, which open in summer. It's hardy across USDA zones 3 through 7 and shrugs off deer. Its summer flowers are a moderate draw for native bees, butterflies, and hummingbirds.
Delphinium — the short answer
Delphinium: grown in zones 3–7.
- USDA zones
- 3–7
- Manual horticultural correction (source not retained); NC State Extension and Missouri Botanical Garden, with the remaining rows from other published sources or Growable Ground compilation
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS and university Extension sources — each tile names its own row's source, because per-field provenance varies.
Score Delphinium on your exact land.
Zone averages can't see the slope, soil, frost, and sun that decide whether delphinium actually takes — and those shift from one yard to the next. Enter your address and we'll score delphinium against your land's real conditions.
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What Delphinium is
Delphinium reaches around five feet at maturity. It blooms in summer. It's also deer-resistant.
How to grow Delphinium
Delphinium grows in USDA zones 3 through 7.
USDA Zones
3-7
USDA PHZM 2023
Soil pH
Data pending
Sun
Data pending
Growable Ground plant catalog
Drainage
Data pending
Growable Ground plant catalog
Mature Height
5 ft
Growable Ground plant catalog
Start the season right
Plant delphinium in full sun.
Match the soil
Pull a soil test from your local Extension lab to confirm pH and drainage match delphinium's needs before planting.
Water steadily
Keep the root zone evenly moist through establishment. Match watering to the plant's drainage preference and your local rainfall.
Harvest at its peak
Cut delphinium blooms in the cool of the morning, just as they open, for the longest display.
Where Delphinium thrives
Delphinium is hardy across USDA zones 3 through 7. Zone is only the starting point, though: the soil pH, drainage, and frost dates on your specific land decide how well it actually does.
A USDA zone is a 10°F band of average annual extreme winter minimum, so zones 3–7 spans average winter lows from -40°F to 10°F (USDA PHZM 2023). Across the 50 states and DC, that band covers 23 outright and splits 25 more down the middle — and which side of that line your land sits on changes the answer.
Zones 3–7·Where Delphinium growsOpen map →
This map is derived from the USDA ARS / PRISM Plant Hardiness Zone Map (2023) and is not the official USDA Plant Hardiness Zone Map.
Where Delphinium stands, state by state
Delphinium is rated for zones 3–7 — a cold floor USDA puts at -40 to -30°F. Across the 50 states and DC, 23 sit fully inside that band, the line runs through 25 more, and 3 sit outside it — and inside every split state, the same line runs on at county grain.
Fully inside zones 3–7
23 states
3 of 23 shown
The line runs through
25 states
- Alaska · zones 1a-9a
- Idaho · zones 3b-8a
- California · zones 4b-11a
3 of 25 shown
Delphinium’s band covers part of each of these states — which side of the line your county sits on changes the answer, and each state page draws it.
State zone extents: USDA Plant Hardiness Zone Map (PHZM) 2023. A zone is a 10°F band of average annual extreme minimum temperature, so a state that splits the band contains the boundary — its own page draws the county line, and a parcel report resolves which side your land sits on.
What grows around Delphinium
Growing guides for delphinium
In rotation planning, delphinium counts as a Other — beds recover best when other crops don’t follow each other in the same spot year over year. (Growable Ground derivation — crop-rotation group from botanical family)
Related plants in perennial flower
Good to know
One caution for pet owners — delphinium is toxic to dogs and cats and horses (severe severity). Keep it out of reach, and call ASPCA Animal Poison Control at (888) 426-4435 in an emergency. (Source: ASPCA.)
Delphinium offers moderate value to bees and other pollinators. (Source: Pollinator Partnership.)
Your land is one point inside Delphinium's range
This page resolves to the species. Your state page draws the county line, and a report reads the parcel — the soil pH, drainage, sun, and frost dates on your exact ground, which no species average can see.
See if Delphinium will thrive on your land
Zone averages are a start. Your exact soil pH, drainage, sun exposure, and frost dates shape whether delphinium actually takes — we score it against the real conditions at your address.
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.
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How we know this about Delphinium
The figures above are cited per row, not per site: the pH band names this plant’s own source column, the three temperature figures each carry their own, and days-to-maturity cites the publication that actually lists it. All of it comes from the Growable Ground Plant Database — a compilation over FAO ECOCROP, USDA PLANTS, and university Extension sources, published openly with per-field provenance.
Grounded inUSDA PLANTS Database•USDA PHZM•ASPCA
Frequently asked questions
Can I grow Delphinium in my zone?
Delphinium grows in USDA hardiness zones 3 through 7 (USDA PHZM 2023). Zone is one factor — soil pH, drainage, and frost dates on your specific parcel also shape whether it takes.
When should you plant Delphinium?
Time delphinium to your own season rather than the calendar. Your local frost dates set the exact window — a Growable Ground report reads them for your address.
What soil does Delphinium need?
Specific pH data for delphinium is pending. A soil test from your local Extension lab confirms what your site needs.
Does Delphinium attract pollinators?
Yes — delphinium's flowers are a solid nectar source for native bees, butterflies, and hummingbirds. (Source: Pollinator Partnership.)
Is Delphinium safe for pets?
Delphinium is toxic to pets (dogs,cats,horses) with severe severity. Keep it out of reach, and call ASPCA Animal Poison Control at (888) 426-4435 in an emergency. (Source: ASPCA.)
Keep exploring Delphinium
Delphinium state by state
Every state delphinium's zone reaches — 3 link straight to that state's delphinium growing page; the rest open the state's full growing guide.