Yes — Strong Match
tithonia (zones 2-11) covers every zone California contains (4b-11a), so hardiness is not what limits it anywhere in the state.
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 tithonia against your parcel's actual hardiness, soil, and sun.
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Zone Comparison
Tithonia Needs
- USDA Zones: 2-11
- Sun: Full Sun
- Mature size: 5 ft tall
- Picking window: ~90 days of harvest
- Drought tolerance: High
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 2-11)
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 Tithonia 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.
When to start the seed
Those dates are when tithonia goes out, not when it starts. It is sown under cover about 6 weeks ahead, so counting back from California's late-side last freeze of Mar 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
California runs as cold as USDA zone 4, and no sourced winter-hardiness floor is on record for tithonia, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether tithonia 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.
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 tithonia survives winter here. Whether the season is long enough — and warm enough — is a different question.
Days to maturity
Tithonia matures in ~80 days (Growable Ground Plant Database). A typical California site has ~317 frost-free days, so plenty of room for a second succession.
Growing degree days
Tithonia needs ~1800 GDD (base 50°F) to ripen. The state median runs ~4290 GDD (from PRISM 1991-2020 climate normals), so California's typical season clears that easily.
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
Tithonia likes near-neutral soil (pH 5.5-7.5). That's the common-ground band across California's alluvial clay and sandy 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 California soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your California 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. California soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Tithonia in California — Quick Answer
- Verdict: Yes — Strong Match
- Plant Zones: 2-11 (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)
- Days to Maturity: 80 days
What Else to Consider for Tithonia 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
What to actually do about these — and the constraints that apply to every California grower, not just tithonia — is covered on the California growing guide.
Timing shifts within California
Tithonia needs about 80 days of frost-free season from planting to harvest. Even Mono County — California’s shortest season at 108 frost-free days — clears that by 28 days, so season length isn’t the constraint anywhere in California. What varies is your own parcel.
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 tithonia about 237 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"). Tithonia's 80-day requirement: USDA PLANTS / Growable Ground plant database (days to maturity). 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 tithonia (USDA PHZM 2023):
Pollinator + Wildlife Value
Tithonia draws honeybees, native bees, butterflies, and hummingbirds (high value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, tithonia 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 tithonia, 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 Tithonia native to California?
No — the USDA PLANTS Database lists Tithonia 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 Tithonia in California
When can I plant Tithonia 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 Tithonia, 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 Tithonia grown in across California?
California spans USDA hardiness zones 4b-11a (USDA ARS PHZM 2023). Tithonia carries a range of zones 2-11, 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). Tithonia 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 Tithonia native to California?
No — the USDA PLANTS Database lists Tithonia 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 Tithonia in California?
Tithonia prefers pH 5.5-7.5 and well (dry spells) drainage (Growable Ground Plant Database). 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 Tithonia actually grow on my specific land in California?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores tithonia 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 tithonia against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that California tithonia averages can't show:
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