Unlikely — Zone Mismatch
four oclock (zones 9-11) does not overlap with District of Columbia's zone range (7b-8a). Growing outdoors is unlikely without significant protection.
One zone short — what would close it
Four Oclock is hardy to zone 9, and the warmest ground in District Of Columbia is zone 8 — 1 zone short. Planted in open ground it will not survive a District Of Columbia winter. To grow it here, grow four oclock in a container and move it under cover for the coldest weeks, or give it a greenhouse.
Season extension and overwintering under cover both work at this margin. How to buy the weeks →
Zone math from 9-11 (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.
District of Columbia spans zones 7b-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 four oclock against your parcel's actual hardiness, soil, and sun.
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Zone Comparison
Four Oclock Needs
- USDA Zones: 9-11
- Frost-Free Days: 210+
- Sun: Full Sun
- Mature size: 3 ft tall
- Picking window: ~60 days of harvest
- Drought tolerance: Medium
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 9-11)
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 Four Oclock 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.
Winter standing
District of Columbia runs as cold as USDA zone 7, and no sourced winter-hardiness floor is on record for four oclock, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether four oclock is a permanent planting or a replant-every-spring crop for you turns on your own zone within District of Columbia; check its hardiness range against that before treating it as long-lived ground.
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 four oclock 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
Four Oclock wants 210+ frost-free days; a typical District of Columbia site sees ~254 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves a workable window — start indoors to bank time.
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
Four Oclock likes near-neutral soil (pH 5.5-7.5). That's the common-ground band across District of Columbia's urban fill and silt loam — a soil test confirms it for your site. It will grow across that whole span, but it does best between pH 6 and 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. Four Oclock needs about 59 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 four oclock 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.
Four Oclock in District of Columbia — Quick Answer
- Verdict: Unlikely — Zone Mismatch
- Plant Zones: 9-11 (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 Four Oclock 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 four oclock here specifically
Four Oclock needs pH 5.5–7.5; 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 four oclock's 5.5–7.5 range. How to handle it →
What to actually do about these — and the constraints that apply to every District of Columbia grower, not just four oclock — is covered on the District of Columbia growing guide.
Pollinator + Wildlife Value
Four Oclock draws moths and hummingbirds (moderate value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, four oclock 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.
Good to Know Before You Plant Four Oclock
Four Oclock is listed as toxic to dogs, cats (seeds, roots) at a mild level (ASPCA). Most listed plants only cause brief upset — a raised bed or a fenced corner usually keeps curious pets clear.
Recommended Four Oclock Varieties for District of Columbia
District of Columbia publishes no state variety trial for four oclock, so we won't invent a "best for District of Columbia" list. Choose types rated to your USDA hardiness zone (7b-8a), and confirm winter survival and drainage against your own parcel.
District of Columbia Cooperative Extension
For District of Columbia-specific cultivar recommendations, planting calendars, and pest pressure for four oclock, 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 Four Oclock native to District of Columbia?
No — the USDA PLANTS Database lists Four Oclock 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 Four Oclock in District of Columbia
When can I plant Four Oclock 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). No sourced winter-hardiness floor is on record for Four Oclock, so this page does not state whether it overwinters in District of Columbia 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 Four Oclock grown in across District of Columbia?
District of Columbia spans USDA hardiness zones 7b-8a (USDA ARS PHZM 2023). Four Oclock carries a range of zones 9-11, 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). Four Oclock needs 210+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Four Oclock native to District of Columbia?
No — the USDA PLANTS Database lists Four Oclock 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 Four Oclock in District of Columbia?
Four Oclock prefers pH 5.5-7.5 and well (dry spells) drainage (FAO ECOCROP). That sits in the common-ground band across District of Columbia soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Four Oclock actually grow on my specific land in District of Columbia?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores four oclock 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 four oclock against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that District of Columbia four oclock 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 four oclock average
Explore More
Growing guides for four oclock
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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