Unlikely — Zone Mismatch
royal poinciana (zones 10-12) does not overlap with Delaware's zone range (7a-8a). Growing outdoors is unlikely without significant protection.
2 zones short — what would close it
Royal Poinciana is hardy to zone 10, and the warmest ground in Delaware is zone 8 — 2 zones short. Planted in open ground it will not survive a Delaware winter. To grow it here, grow royal poinciana in an earth-sheltered greenhouse — its modeled 2.5-zone lift covers this gap.
An earth-sheltered greenhouse is the lift this needs. How a greenhouse changes what you can grow →
Zone math from 10-12 (plant) against 7-8 (Delaware). Lift modeled by crop_engine.GREENHOUSE_ZONE_MODIFIER_BY_SUBTYPE['earth_sheltered'] (+2.5 zones) via api/fast_sections.py Unlock Engine v2.
Royal Poinciana in Delaware — the short answer
Royal Poinciana in Delaware: hardy in zones 10–12, full sun.
- Plant zones
- 10-12
- Not verified
- Delaware zones
- 7a-8a
- USDA PHZM 2023
- Frost window
- Mar 23 - Mar 23 – Nov 17 - Nov 19
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 238 days
- NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS and university Extension sources — per-field provenance varies and is published with the dataset.
Your yard isn't the whole zone.
Delaware spans zones 7a-8a, but your yard sits in exactly one — and slope, tree cover, and cold-air pockets nudge it further. Enter your address and we'll score royal poinciana against your parcel's actual hardiness, soil, and sun.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
No card required · your parcel report in seconds — read in full free for your first 14 days
Where Royal Poinciana Stands in Delaware
Royal Poinciana is rated for zones 10–12 — a cold floor USDA puts at 30 to 40°F. No Delaware county sits inside it, so in open ground this is a grown-under-cover plant here rather than a bed plant — which is a statement about Delaware winters, not about royal poinciana.
Below the zone 10 floor
3 counties
- Kent County · zone 7b
- New Castle County · zone 7b
- Sussex County · zone 7b
Winter cold is the limit here — the same plant works in a container that comes under cover.
County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. A zone is a 10°F band of average annual extreme minimum temperature, so the floor above is the band the plant's rating denotes, not a single measured kill point. Slope, shelter and cold-air drainage routinely move a site half a zone either way from its county figure — which is the part only your address resolves.
Zone Comparison
Royal Poinciana Needs
- USDA Zones: 10-12
- Sun: Full Sun
- Mature size: 40 ft tallWe haven't confirmed this against a published source yet.
- Drought tolerance: Medium
Delaware Has
- USDA Zones: 7a-8a
- Last Hard Freeze (28°F): Mar 23 - Mar 23
- First Hard Freeze (28°F): Nov 17 - Nov 19
- Annual Rainfall: 42-48 inches
- Common Soils: Sandy loam, Silt loam, Tidal marsh
Plant Zone Range (zones 10-12)
Preferred Soil pH
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS, and university Extension sources — per-field provenance varies and is published with the dataset. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Royal Poinciana in Delaware
The frost window
Across Delaware, the last spring hard freeze (28°F) clears between Mar 23 and Mar 23, and the first fall hard freeze lands between Nov 17 and Nov 19 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 239-day window you can count on — up to 241 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.
Winter standing
Delaware runs as cold as USDA zone 7, and no sourced winter-hardiness floor is on record for royal poinciana, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether royal poinciana is a permanent planting or a replant-every-spring crop for you turns on your own zone within Delaware; check its hardiness range against that before treating it as long-lived ground.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: Growable Ground Plant Database — frost-free days from FAO ECOCROP, days to harvest from university Extension production guides, and growing-degree-day and chill-hour minimums that are compilation estimates rather than published figures. Your site's own frost dates can run earlier or later than the state range — a parcel report pins them down.
Growing Season Fit
The zone check says royal poinciana does not survive a Delaware winter in the ground. The season figures below measure a different question — whether it could finish a season here at all — and they only bear on Delaware under protection.
Chill hours
Royal Poinciana has no winter-chill requirement — its listed minimum is 0 hours (Growable Ground Plant Database). Delaware typically banks ~2500 chill hours per winter (from PRISM 1991-2020 climate normals), so chill is not a constraint on this plant here — and not evidence in its favour either. Winter survival and season length are what decide it.
GDD and chill-hour figures are computed from PRISM 1991-2020 monthly climate normals; frost-free days from NOAA Regional Climate Centers ACIS, 1991-2020. Each is the state median across its counties (P25/P75 span the within-state spread). Hardiness-zone range is USDA PHZM 2023.
Soil + Drainage Fit
Royal Poinciana tolerates a wide pH range (pH 4.5-7.5) — 3 units, acid ground through alkaline — so soil acidity is rarely what limits it in Delaware. A soil test is still worth having, but for what else it tells you about this site, not to clear this plant. It will grow across that whole span, but it does best between pH 5.5 and 6.5 — worth knowing before you decide whether a Delaware soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Delaware site is heavier clay or sits in a low spot, a raised bed lifts the roots above wet ground, or work in compost.
Your land, not the state average
SSURGO maps about 19.8% of Delaware as poorly or somewhat-poorly drained, and the class flips parcel to parcel. Royal Poinciana sits mid-range for drought tolerance, so either extreme can cost you — your soil map unit, not the state average, is the real answer.
Check your parcel → Source: USDA NRCS SSURGO.
Plant pH requirements: FAO ECOCROP and USDA PLANTS, with the remaining rows from other published sources or Growable Ground compilation. Drainage: FAO ECOCROP, with the remaining rows from other published sources or Growable Ground compilation. Delaware soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
What Else to Consider for Royal Poinciana in Delaware
Zone compatibility tells you about winter cold survival — but Delaware growers also need to think about:
Sandy soils in southern DE drain too quickly
Salt spray damage near the coast
Rising water tables in low-lying areas
Growing royal poinciana here specifically
Royal Poinciana roots run medium and prefer pH 4.5–7.5, but drainage comes first here: SSURGO maps about 19.8% of Delaware as poorly or somewhat-poorly drained, and wet ground rots its crown before pH ever matters.
Plant royal poinciana on a raised, gravel-amended berm so water drains fast and the crown stays dry. How to handle it →
What to actually do about these — and the constraints that apply to every Delaware grower, not just royal poinciana — is covered on the Delaware growing guide.
Where in Delaware Royal Poinciana Is Zone-Hardy
Royal Poinciana is rated for USDA zones 10–12. No Delaware county reaches it. Even Sussex County, the state’s mildest winter at zone 7b, sits below the plant’s zone 10 floor — so in open ground this one needs winter protection here, or a container that comes under cover.
County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. Royal Poinciana’s zone 10–12 band: Not verified. A parcel report resolves your address’s own zone and frost dates rather than its county’s.
Pollinator + Wildlife Value
Royal Poinciana draws honeybees, native bees, and butterflies (moderate value). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, royal poinciana can only work that bloom inside Delaware's frost window — roughly 241 days, opening after the last 28°F freeze (Mar 23 - Mar 23) and closing at the first (Nov 17 - Nov 19), per NOAA Regional Climate Centers ACIS, 1991-2020. Pollinator value: We haven't confirmed this against a published source yet.
Good to Know Before You Plant Royal Poinciana
Royal Poinciana is listed as toxic to dogs, cats (seeds, pods) at a mild level. (Source: Pet Poison Helpline.) Most listed plants only cause brief upset — a raised bed or a fenced corner usually keeps curious pets clear.
Delaware Cooperative Extension
For Delaware-specific cultivar recommendations, planting calendars, and pest pressure for royal poinciana, the canonical source is University of Delaware Cooperative Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Royal Poinciana native to Delaware?
No — the USDA PLANTS Database lists Royal Poinciana as introduced rather than native in the Lower 48, so it is not part of Delaware's native flora. It grows here as a garden plant; pairing it with a few Delaware natives keeps local pollinators fed too.
Looking for plants that belong here? The Delaware growing guide lists plants that USDA PLANTS records growing in Delaware and that Kew and NatureServe Explorer both list in its native range, leaving out any that NatureServe flags as exotic there or that our audit holds.
State records: USDA PLANTS Database state-distribution data (presence, not state-level nativity), accessed 2026-10-19.
Common Questions About Growing Royal Poinciana in Delaware
When can I plant Royal Poinciana in Delaware?
Delaware's last spring hard freeze (28°F) clears between Mar 23 and Mar 23, and the first fall hard freeze lands between Nov 17 and Nov 19 (NOAA Regional Climate Centers ACIS, 1991-2020). No sourced winter-hardiness floor is on record for Royal Poinciana, so this page does not state whether it overwinters in Delaware and publishes no fall establishment date for it — check its hardiness range against your own zone before treating it as a permanent planting.
What hardiness zone is Royal Poinciana grown in across Delaware?
Delaware spans USDA hardiness zones 7a-8a (USDA ARS PHZM 2023). Royal Poinciana is listed for zones 10-12, which do not overlap them, so there is no zone in Delaware where this page can call outdoor growing reliable. A parcel report resolves your own address's zone.
How many frost-free days does a typical Delaware site have?
A typical Delaware site sees ~241 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Royal Poinciana needs 180+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Royal Poinciana native to Delaware?
No — the USDA PLANTS Database lists Royal Poinciana as introduced rather than native in the Lower 48, so it is not part of Delaware's native flora. It grows here as a garden plant; pairing it with a few Delaware natives keeps local pollinators fed too.
How should I amend the soil for Royal Poinciana in Delaware?
Royal Poinciana tolerates pH 4.5-7.5 and well (dry spells) drainage (FAO ECOCROP). That is a 3-unit span, acid ground through alkaline, so pH is rarely what limits this plant on a Delaware site — amend for drainage and organic matter first.
Will Royal Poinciana actually grow on my specific land in Delaware?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores royal poinciana against your address's mapped soil pH, drainage, sun, and frost-date data drawn from USDA SSURGO, NOAA, and PRISM — not state averages.
Check your specific parcel in Delaware
State-level data is a sketch. Your Growable Ground report scores royal poinciana against your land's mapped soil, modelled sun, drainage, and frost data — not zone averages.
Three things about your lot that Delaware royal poinciana averages can't show:
We read public map data around Delaware — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Delaware royal poinciana average
Explore More
Growing guides for royal poinciana
Explore Delaware county by county
Delaware carries 3 counties with their own USDA zone — a sample of the growing pages for royal poinciana there:
Where else royal poinciana grows
Royal Poinciana's zone band crosses state lines — these are the states closest to Delaware in winter climate where it also has a page, plus the far ends of its range. Each one re-answers the question with that state's own record.
More to grow in Delaware
Delaware has a growing page for 1,005 plants — a rotating sample of the rest of the shelf.
Analysis by the Growable Ground research team, grounded in USDA PLANTS, USDA NRCS SSURGO, NOAA Climate Normals (1991-2020), and named Cooperative Extension sources. How we know →
Cite this dataset
Kirchick, M. (2026). Growable Ground Plant Database [Data set]. Zenodo. https://doi.org/10.5281/zenodo.21435643
Licensed CC BY-NC 4.0. DOI 10.5281/zenodo.21435643
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