Conditional — Some Areas
Zone data for penstemon is not yet available. Growing may be possible depending on your specific location.
Zone Comparison
Penstemon Needs
- USDA Zones: Data pending
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 data: USDA PLANTS Database / plant_species_v5.csv. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
Penstemon in Colorado — Quick Answer
- Verdict: Conditional — Some Areas
- Plant Zones: Data pending (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
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
Pollinator + Wildlife Value
Penstemon draws pollinators (high value, USDA PLANTS Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Deer pressure is meaningful across much of Colorado; penstemon is listed as deer-resistant (USDA PLANTS Database), which makes it a safer pick for unfenced sites.
Colorado Cooperative Extension
For Colorado-specific cultivar recommendations, planting calendars, and pest pressure for penstemon, the canonical source is Colorado State University Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Check your specific parcel in Colorado
State-level data is a sketch. Your Growable Ground report scores penstemon against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
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