Generally — Most Areas
spirea (zones 5-11) suits most of California (4b-11a) — zones 5-11 are in range, and the rest of the state is the exception.
Your yard isn't the whole zone.
California spans zones 4b-11a, 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 spirea against your parcel's actual hardiness, soil, and sun.
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Zone Comparison
Spirea Needs
- USDA Zones: 5-11
- Frost-Free Days: 145+
- Sun: Part Sun
- Mature size: 4 ft tall
- Drought tolerance: Medium
California Has
- USDA Zones: 4b-11a
- Last Hard Freeze (28°F): Jan 19 - Mar 19
- First Hard Freeze (28°F): Nov 29 - Dec 12
- Annual Rainfall: 5-80 inches
- Common Soils: Alluvial clay, Sandy loam, Adobe clay
Plant Zone Range (zones 5-11)
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 Spirea in California
The frost window
Across California, the last spring hard freeze (28°F) clears between Jan 19 and Mar 19, and the first fall hard freeze lands between Nov 29 and Dec 12 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 255-day window you can count on — up to 327 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
California runs as cold as USDA zone 4, and no sourced winter-hardiness floor is on record for spirea, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether spirea is a permanent planting or a replant-every-spring crop for you turns on your own zone within California; check its hardiness range against that before treating it as long-lived ground.
Timing tuned to sub-state frost dates — Mono County, not the statewide average.
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 spirea survives winter in part of California, not across all of it. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
Spirea wants 145+ frost-free days; a typical California site sees ~317 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves comfortable headroom for succession planting.
Chill hours
Spirea requires ~500 chill hours (32-45°F dormancy window). California typically banks ~1172 chill hours per winter (from PRISM 1991-2020 climate normals), which keeps this plant on track.
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
Spirea likes near-neutral soil (pH 5-6.8). That's the common-ground band across California's alluvial clay and sandy loam — a soil test confirms it for your site.
Your land, not the state average
California's soils run mostly loam, but SSURGO maps the series, texture, and drainage under your exact parcel. What matters for spirea is the horizon its roots actually work, not the surface. That map unit, not the state average, decides how spirea performs.
Check your parcel → Source: USDA NRCS SSURGO.
Plant pH and drainage requirements from USDA PLANTS Database. California soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Spirea in California — Quick Answer
- Verdict: Generally — Most Areas
- Plant Zones: 5-11 (USDA PLANTS Database)
- State Zones: 4b-11a (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Jan 19 - Mar 19 to Nov 29 - Dec 12 (NOAA Regional Climate Centers ACIS, 1991-2020)
What Else to Consider for Spirea in California
Zone compatibility tells you about winter cold survival — but California growers also need to think about:
Drought is a persistent challenge — irrigation is essential in most regions
Wildfire risk affects rural and foothill properties
Adobe clay soils in valleys drain poorly without amendment
Wide climate variation means plant selection is highly location-specific
Growing spirea here specifically
California's soils run mostly loam (Alfisols), and whether that suits spirea's pH 5.0–6.8 preference comes down to your exact parcel, not the statewide picture.
Pull your parcel's SSURGO map unit, test pH, and amend toward spirea's 5.0–6.8 target before planting. How to handle it →
What to actually do about these — and the constraints that apply to every California grower, not just spirea — is covered on the California growing guide.
Timing shifts within California
California isn't one climate. In Mono County, the last hard freeze (28°F) holds until about Jun 4 — roughly 120 days later than the recorded state median — so plant spirea to your county's window, not the statewide date.
Spirea needs about 145 days of frost-free season to complete its cycle. 53 of California’s 57 counties give it that outright. The tightest that does is Plumas County at 158 frost-free days — 13 to spare. Below that line you are transplanting or extending the season, not direct-sowing.
Across California’s 57 counties the frost-free season runs from 108 days in Mono County to 365 days in Ventura County — a spread of 257 days, which is why a single statewide planting date misleads. The median California county sees 317 frost-free days, leaving spirea about 172 days of slack on a typical parcel — room for a second sowing where the season runs long.
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"). Spirea's 145-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Where in California Fits Best
Even within California's zones 4b-11a, county microclimates differ enough to change what thrives. These counties carry the closest zone match for spirea (USDA PHZM 2023):
Pollinator + Wildlife Value
Spirea draws honeybees, native bees, and butterflies (moderate value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, spirea can only work that bloom inside California's frost window — roughly 317 days, opening after the last 28°F freeze (Jan 19 - Mar 19) and closing at the first (Nov 29 - Dec 12), per NOAA Regional Climate Centers ACIS, 1991-2020.
California Cooperative Extension
For California-specific cultivar recommendations, planting calendars, and pest pressure for spirea, the canonical source is UC Agriculture and Natural Resources. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Spirea native to California?
No — the USDA PLANTS Database lists Spirea as introduced rather than native in the Lower 48, so it is not part of California's native flora. It grows here as a garden plant; pairing it with a few California natives keeps local pollinators fed too.
Looking for plants that belong here? The California 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 Spirea in California
When can I plant Spirea in California?
California's last spring hard freeze (28°F) clears between Jan 19 and Mar 19, and the first fall hard freeze lands between Nov 29 and Dec 12 (NOAA Regional Climate Centers ACIS, 1991-2020). No sourced winter-hardiness floor is on record for Spirea, so this page does not state whether it overwinters in California 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 Spirea grown in across California?
California spans USDA hardiness zones 4b-11a (USDA ARS PHZM 2023). Spirea carries a range of zones 5-11, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical California site have?
A typical California site sees ~317 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Spirea needs 145+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date. In cooler counties like Mono, the freeze-free season runs shorter than the state average, so verify your own county's window.
Is Spirea native to California?
No — the USDA PLANTS Database lists Spirea as introduced rather than native in the Lower 48, so it is not part of California's native flora. It grows here as a garden plant; pairing it with a few California natives keeps local pollinators fed too.
How should I amend the soil for Spirea in California?
Spirea prefers pH 5-6.8 (USDA PLANTS). That sits in the common-ground band across California soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Spirea actually grow on my specific land in California?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores spirea 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 California
State-level data is a sketch. Your Growable Ground report scores spirea against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that California spirea averages can't show:
We read public map data around California — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the California spirea average
Explore More
Growing guides for spirea
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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