Growing cosmos in zone 5b
(Zone 5b = an average winter low of -15°F to -10°F.)
In USDA zone 5b, the typical last spring frost is May 1 and the first fall frost is October 10. Here is when to plant cosmos against those dates.
Typical timing
Zone 5b planting schedule
Evidence trail
How these dates are built
Sprout applies the cited planting offsets to the typical zone 5b frost anchors. The result is a planning baseline for the zone, not a local weather forecast.
- USDA Plant Hardiness Zone Map, 2023USDA Agricultural Research Service / Oregon State University PRISM Group. Supports the USDA hardiness-zone band.
- U.S. Climate Normals 1991-2020NOAA National Centers for Environmental Information. Supports the median spring and fall freeze dates.
- Cosmos in the GardenUtah State University Extension. Supports direct-sowing timing (normalized).
Method note
Direct-sow timing (sow once all danger of frost has passed; start-only anchor expressed as weeks 0-2), 1/8 inch seed depth, spacing 1 to 2 feet (12 to 24 in), full sun (8+ hours), problems (heavy self-seeding, weed competition during establishment). Soil pH is given qualitatively (neutral to slightly alkaline) with no numeric range, so soilPh is omitted. Water is given as deep watering once per week with no inch rate, so waterInchesPerWeek is omitted.
These are zone 5b averages
Computed from 2,843 ZIP codes in zone 5b. Your town's frost dates vary; enter your ZIP for dates built on your nearest weather station.
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Put these dates to work
The plant profile covers spacing, light, water, soil, and source-backed timing details.