Generally — Most Areas
woodland phlox (zones 4-10) partially overlaps with Colorado (3a-7a). It can grow in zones 4-7 within the state.
Your yard isn't the whole zone.
Colorado spans zones 3a-7a, 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 woodland phlox against your parcel's actual hardiness, soil, and sun.
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Zone Comparison
Woodland Phlox Needs
- USDA Zones: 4-10
- Soil pH: 5.5 - 7.2
- Sun: Part Sun
- Frost-Free Days: 100+
Colorado Has
- USDA Zones: 3a-7a
- Last Frost: Apr 15 - Jun 15
- First Frost: Aug 25 - Oct 15
- Annual Rainfall: 7-20 inches
- Common Soils: Sandy loam, Clay loam, Alkaline caliche
Plant Zone Range (zones 4-10)
Preferred Soil pH
Plant data: USDA PLANTS Database / plant_species_v5.csv. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Woodland Phlox in Colorado
The frost window
Across Colorado, the last spring frost clears between Apr 15 and Jun 15, and the first fall frost lands between Aug 25 and Oct 15 (NOAA Climate Normals 1991-2020). Counting from the latest last frost to the earliest first frost, that's a 71-day window you can count on — up to 183 days on a mild site in a kind year.
Frost hardiness
Woodland Phlox is cold-hardy to -33°F (USDA PLANTS Database), so you can plant on the early side of Colorado's window — even a few weeks before the final frost date.
Establishment timing
As a long-lived plant, woodland phlox isn't racing the calendar to a harvest date. Plant it in spring once the last-frost window passes so roots settle in through the full season, or in early fall while the soil still holds summer warmth.
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
Zone compatibility says you can survive winter here. Whether the growing season is long enough — and warm enough — is a different question.
Frost-free days
Woodland Phlox wants 100+ frost-free days; a typical Colorado site sees ~190 (NOAA Climate Normals). That leaves comfortable headroom for succession planting.
Climate aggregates derive from USDA NRCS county-level hardiness data + Cornell CALS Extension GDD-by-region tables + MSU Extension chill-hours-by-zone (1991-2020 NOAA Climate Normals baseline).
Soil + Drainage Fit
Woodland Phlox likes near-neutral soil (pH 5.5-7.2). That's the common-ground band across Colorado's sandy loam and clay loam — a soil test confirms it for your site.
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.
Woodland Phlox in Colorado — Quick Answer
- Verdict: Generally — Most Areas
- Plant Zones: 4-10 (USDA PLANTS Database)
- State Zones: 3a-7a (USDA ARS PHZM 2023)
- Growing Season: Apr 15 - Jun 15 to Aug 25 - Oct 15 (NOAA Climate Normals)
What Else to Consider
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
Build the irrigation first — drip plus mulch makes a high-desert garden run on remarkably little water.
High altitude UV and temperature swings stress plants
Harden transplants gradually, shade-cloth their first high-sun week, and keep row covers handy for cold nights.
Very short growing season at elevation (60-90 frost-free days above 8,000 ft)
Above 8,000 feet, count your real frost-free days and choose varieties bred to finish inside them.
Alkaline soils (pH 7.5-8.5) limit acid-loving plants without amendment
A soil test tells you your actual pH — grow acid-lovers in containers of amended mix while the native ground grows everything else.
Pollinator + Wildlife Value
Woodland Phlox draws pollinators (high value, USDA PLANTS Database). Planting it near vegetable beds can lift fruit set on neighboring crops.
Colorado Cooperative Extension
For Colorado-specific cultivar recommendations, planting calendars, and pest pressure for woodland phlox, the canonical source is Colorado State University Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Woodland Phlox native to Colorado?
Woodland Phlox 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 Woodland Phlox in Colorado
When can I plant Woodland Phlox in Colorado?
Colorado's last spring frost clears between Apr 15 and Jun 15, and the first fall frost lands between Aug 25 and Oct 15 (NOAA Climate Normals 1991-2020). Woodland Phlox is a long-lived planting, so target spring just after your local last frost — or early fall while the soil holds warmth — and let it establish through the season.
What hardiness zone is Woodland Phlox grown in across Colorado?
Colorado spans USDA hardiness zones 3a-7a (USDA ARS PHZM 2023). Woodland Phlox carries a range of zones 4-10, 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 ~190 frost-free days per year (derived from NOAA Climate Normals 1991-2020). Woodland Phlox needs 100+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Woodland Phlox native to Colorado?
Woodland Phlox 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 Woodland Phlox in Colorado?
Woodland Phlox prefers pH 5.5-7.2 (USDA PLANTS 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 Woodland Phlox actually grow on my specific land in Colorado?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores woodland phlox 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 woodland phlox against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
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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