Unlikely — Zone Mismatch
calopo (zones 10-12) does not overlap with District of Columbia's zone range (7b-8a). Growing outdoors is unlikely without significant protection.
2 zones short — what would close it
Calopo is hardy to zone 10, and the warmest ground in District Of Columbia is zone 8 — 2 zones short. Planted in open ground it will not survive a District Of Columbia winter. To grow it here, grow calopo under glass — a greenhouse is the only lift this wide the engine models.
A greenhouse is the lift this needs. How a greenhouse changes what you can grow →
Zone math from 10-12 (plant) against 7-8 (District of Columbia). Lift modeled by crop_engine Sprint 20B effective_zone_modifier (+2 zones) via api/fast_sections.py Unlock Engine v2.
Your yard isn't the whole zone.
Calopo is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is. A typical District of Columbia site runs ~254 frost-free days, but that is a state median, not your yard: slope, trees, and low spots move the last-frost date across a single parcel. Enter your address and we'll score calopo against your land's actual frost dates, sun, and soil.
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Zone Comparison
Calopo Needs
- USDA Zones: 10-12
- Frost-Free Days: 120+
- Sun: Full Sun
- Mature size: 1 ft tall
- Drought tolerance: Low
District of Columbia Has
- USDA Zones: 7b-8a
- Last Hard Freeze (28°F): Mar 15
- First Hard Freeze (28°F): Nov 24
- Annual Rainfall: 39-43 inches
- Common Soils: Urban fill, Silt loam, Clay loam
Plant Zone Range (zones 10-12)
Preferred Soil pH
Plant data: USDA PLANTS Database / Growable Ground plant catalog. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Calopo in District of Columbia
The frost window
Across District of Columbia, the last spring hard freeze (28°F) clears between Mar 15 and Mar 15, and the first fall hard freeze lands between Nov 24 and Nov 24 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 254-day window you can count on — up to 254 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.
Frost tenderness
Calopo is frost-tender — its listed minimum temperature is 64.4°F (USDA PLANTS Database) — so set plants out two to three weeks PAST your local last hard freeze, not on it and not on the state's earliest date. The 28°F marker above is when killing freezes stop, not when light frost does.
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.
Growing Season Fit
The zone check says calopo does not survive a District of Columbia 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 District of Columbia under protection.
Frost-free days
Calopo wants 120+ frost-free days; a typical District of Columbia site sees ~254 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves comfortable headroom for succession planting.
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
Calopo tolerates a wide pH range (pH 4.3-8) — 3.7 units, acid ground through alkaline — so soil acidity is rarely what limits it in District of Columbia. 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 4.5 and 5.7 — worth knowing before you decide whether a District of Columbia soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your District of Columbia site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Your land, not the state average
District Of Columbia's soils run mostly silt loam, but SSURGO maps the series, texture, and drainage under your exact parcel. Calopo needs about 7 inches of workable depth, so it is that horizon — not the surface — you are testing for. That map unit, not the state average, decides how calopo performs.
Check your parcel → Source: USDA NRCS SSURGO.
Plant pH and drainage requirements from USDA PLANTS Database. District of Columbia soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Calopo in District of Columbia — Quick Answer
- Verdict: Unlikely — Zone Mismatch
- Plant Zones: 10-12 (USDA PLANTS Database)
- State Zones: 7b-8a (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Mar 15 to Nov 24 (NOAA Regional Climate Centers ACIS, 1991-2020)
What Else to Consider for Calopo in District of Columbia
Zone compatibility tells you about winter cold survival — but District of Columbia growers also need to think about:
Dense urban siting means small lots, compacted fill soils, and limited sun
Summer heat and humidity promote fungal diseases
The urban heat-island effect pushes summer temperatures above surrounding suburbs
Growing calopo here specifically
Calopo needs pH 4.3–8.0; District Of Columbia's dominant silt loam soils may or may not deliver that, so your parcel's SSURGO map unit is the real test.
Start with a soil test on your own ground and adjust pH and texture to fit calopo's 4.3–8.0 range. How to handle it →
What to actually do about these — and the constraints that apply to every District of Columbia grower, not just calopo — is covered on the District of Columbia growing guide.
Pollinator + Wildlife Value
Calopo draws honeybees (low value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, calopo can only work that bloom inside District of Columbia's frost window — roughly 254 days, opening after the last 28°F freeze (Mar 15) and closing at the first (Nov 24), per NOAA Regional Climate Centers ACIS, 1991-2020.
District of Columbia Cooperative Extension
For District of Columbia-specific cultivar recommendations, planting calendars, and pest pressure for calopo, the canonical source is UDC Center for Urban Agriculture. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Calopo native to District of Columbia?
No — the USDA PLANTS Database lists Calopo as introduced rather than native in the Lower 48, so it is not part of District of Columbia's native flora. It grows here as a garden plant; pairing it with a few District of Columbia natives keeps local pollinators fed too.
Looking for plants that belong here? The District of Columbia 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 Calopo in District of Columbia
When can I plant Calopo in District of Columbia?
District of Columbia's last spring hard freeze (28°F) clears between Mar 15 and Mar 15, and the first fall hard freeze lands between Nov 24 and Nov 24 (NOAA Regional Climate Centers ACIS, 1991-2020). Calopo is frost-tender — its listed minimum temperature is 64.4°F (USDA PLANTS Database) — so wait two to three weeks past your site's last hard freeze, when light frost has also stopped, before planting out.
What hardiness zone is Calopo grown in across District of Columbia?
District of Columbia spans USDA hardiness zones 7b-8a (USDA ARS PHZM 2023). Calopo carries a range of zones 10-12, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical District of Columbia site have?
A typical District of Columbia site sees ~254 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Calopo needs 120+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Calopo native to District of Columbia?
No — the USDA PLANTS Database lists Calopo as introduced rather than native in the Lower 48, so it is not part of District of Columbia's native flora. It grows here as a garden plant; pairing it with a few District of Columbia natives keeps local pollinators fed too.
How should I amend the soil for Calopo in District of Columbia?
Calopo tolerates pH 4.3-8 and well (dry spells) drainage (FAO ECOCROP). That is a 3.7-unit span, acid ground through alkaline, so pH is rarely what limits this plant on a District of Columbia site — amend for drainage and organic matter first.
Will Calopo actually grow on my specific land in District of Columbia?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores calopo 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 District of Columbia
State-level data is a sketch. Your Growable Ground report scores calopo against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that District of Columbia calopo averages can't show:
We read public map data around District of Columbia — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the District of Columbia calopo average
Explore More
Growing guides for calopo
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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