Generally — Most Areas
passionflower (zones 5-9) suits most of Colorado (3b-7b) — zones 5-7 are in range, and the rest of the state is the exception.
Your yard isn't the whole zone.
Colorado spans zones 3b-7b, 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 passionflower against your parcel's actual hardiness, soil, and sun.
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Zone Comparison
Passionflower Needs
- USDA Zones: 5-9
- Sun: Full Sun
- Mature size: 8 ft tall
- Picking window: ~60 days of harvest
- Drought tolerance: Medium
Colorado Has
- USDA Zones: 3b-7b
- Last Hard Freeze (28°F): Apr 25 - May 19
- First Hard Freeze (28°F): Sep 29 - Oct 16
- Annual Rainfall: 7-20 inches
- Common Soils: Sandy loam, Clay loam, Alkaline caliche
Plant Zone Range (zones 5-9)
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 Passionflower in Colorado
The frost window
Across Colorado, the last spring hard freeze (28°F) clears between Apr 25 and May 19, and the first fall hard freeze lands between Sep 29 and Oct 16 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 133-day window you can count on — up to 174 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 passionflower goes out, not when it starts. It is sown under cover about 12 weeks ahead, so counting back from Colorado's late-side last freeze of May 19 is what fixes your sowing date — and a yard that clears frost earlier than the state's late date starts earlier still.
Winter standing
Colorado runs as cold as USDA zone 3, and no sourced winter-hardiness floor is on record for passionflower, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether passionflower is a permanent planting or a replant-every-spring crop for you turns on your own zone within Colorado; 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 passionflower survives winter in part of Colorado, not across all of it. Whether the season is long enough — and warm enough — is a different question.
Days to maturity
Passionflower matures in ~180 days (Growable Ground Plant Database). A typical Colorado site has ~155 frost-free days, so tight — start indoors or use season-extension to close the gap.
Growing degree days
Passionflower needs ~2500 GDD (base 50°F) to ripen. The state median runs ~2083 GDD (from PRISM 1991-2020 climate normals), so Colorado's typical season runs short on heat — pick a south-facing site and consider season extension.
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
Passionflower likes near-neutral soil (pH 5.5-7.5). That's the common-ground band across Colorado's sandy loam and clay 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 Colorado soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Colorado site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Plant pH and drainage requirements from USDA PLANTS Database. Colorado soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Passionflower in Colorado — Quick Answer
- Verdict: Generally — Most Areas
- Plant Zones: 5-9 (USDA PLANTS Database)
- State Zones: 3b-7b (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Apr 25 - May 19 to Sep 29 - Oct 16 (NOAA Regional Climate Centers ACIS, 1991-2020)
- Days to Maturity: 180 days
What Else to Consider for Passionflower in Colorado
Zone compatibility tells you about winter cold survival — but Colorado growers also need to think about:
Low annual rainfall (7-20 inches) means irrigation is essential nearly everywhere
High altitude UV and temperature swings stress plants
Very short growing season at elevation (60-90 frost-free days above 8,000 ft)
Alkaline soils (pH 7.5-8.5) limit acid-loving plants without amendment
What to actually do about these — and the constraints that apply to every Colorado grower, not just passionflower — is covered on the Colorado growing guide.
Timing shifts within Colorado
Passionflower needs about 180 days of frost-free season from planting to harvest. 11 of Colorado’s 64 counties give it that outright. The tightest that does is Denver County at 183 frost-free days — 3 to spare. Below that line you are transplanting or extending the season, not direct-sowing.
Across Colorado’s 64 counties the frost-free season runs from 85 days in Chaffee County to 209 days in Mesa County — a spread of 124 days, which is why a single statewide planting date misleads. The median Colorado county sees 155 frost-free days, which is 25 days short of what passionflower needs — so on a typical Colorado parcel this is a transplant-or-protect crop, not a direct-sow one.
County last-freeze dates and frost-free day counts: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F freeze (earlier than the folk 32°F "last frost"). Passionflower's 180-day requirement: USDA PLANTS / Growable Ground plant database (days to maturity). A parcel report resolves your address's own frost dates.
Where in Colorado Fits Best
Even within Colorado's zones 3b-7b, county microclimates differ enough to change what thrives. These counties carry the closest zone match for passionflower (USDA PHZM 2023):
Pollinator + Wildlife Value
Passionflower draws native bees and butterflies (high value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, passionflower can only work that bloom inside Colorado's frost window — roughly 155 days, opening after the last 28°F freeze (Apr 25 - May 19) and closing at the first (Sep 29 - Oct 16), per NOAA Regional Climate Centers ACIS, 1991-2020.
Colorado Cooperative Extension
For Colorado-specific cultivar recommendations, planting calendars, and pest pressure for passionflower, the canonical source is Colorado State University Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Passionflower native to Colorado?
Passionflower is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in Colorado. It can still earn a place in a Colorado garden — the zone comparison above tells you whether it will thrive.
Looking for plants that belong here? The Colorado 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 Passionflower in Colorado
When can I plant Passionflower in Colorado?
Colorado's last spring hard freeze (28°F) clears between Apr 25 and May 19, and the first fall hard freeze lands between Sep 29 and Oct 16 (NOAA Regional Climate Centers ACIS, 1991-2020). No sourced winter-hardiness floor is on record for Passionflower, so this page does not state whether it overwinters in Colorado 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 Passionflower grown in across Colorado?
Colorado spans USDA hardiness zones 3b-7b (USDA ARS PHZM 2023). Passionflower carries a range of zones 5-9, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Colorado site have?
A typical Colorado site sees ~155 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Passionflower 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 Passionflower native to Colorado?
Passionflower is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in Colorado. It can still earn a place in a Colorado garden — the zone comparison above tells you whether it will thrive.
How should I amend the soil for Passionflower in Colorado?
Passionflower prefers pH 5.5-7.5 and well (dry spells) drainage (Growable Ground Plant Database). That sits in the common-ground band across Colorado soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Passionflower actually grow on my specific land in Colorado?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores passionflower 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 Colorado
State-level data is a sketch. Your Growable Ground report scores passionflower against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Colorado passionflower averages can't show:
We read public map data around Colorado — soil, climate, flood, and parcel records. How we handle your address.
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