Generally — Most Areas
horehound (zones 3-9) suits most of Arizona (5b-10b) — zones 5-9 are in range, and the rest of the state is the exception.
Your yard isn't the whole zone.
Arizona spans zones 5b-10b, 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 horehound against your parcel's actual hardiness, soil, and sun.
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Zone Comparison
Horehound Needs
- USDA Zones: 3-9
- Frost-Free Days: 90+
- Sun: Full Sun
- Mature size: 2 ft tall
- Picking window: ~90 days of harvest
- Drought tolerance: High
Arizona Has
- USDA Zones: 5b-10b
- Last Hard Freeze (28°F): Feb 1 - Apr 2
- First Hard Freeze (28°F): Nov 13 - Dec 12
- Annual Rainfall: 3-25 inches
- Common Soils: Caliche, Sandy loam, Desert pavement
Plant Zone Range (zones 3-9)
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 Horehound in Arizona
The frost window
Across Arizona, the last spring hard freeze (28°F) clears between Feb 1 and Apr 2, and the first fall hard freeze lands between Nov 13 and Dec 12 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 225-day window you can count on — up to 314 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 horehound goes out, not when it starts. It is sown under cover about 8 weeks ahead, so counting back from Arizona's late-side last freeze of Apr 2 is what fixes your sowing date — and a yard that clears frost earlier than the state's late date starts earlier still.
Winter standing
Arizona runs as cold as USDA zone 5, and no sourced winter-hardiness floor is on record for horehound, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether horehound is a permanent planting or a replant-every-spring crop for you turns on your own zone within Arizona; 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 horehound survives winter in part of Arizona, not across all of it. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
Horehound wants 90+ frost-free days; a typical Arizona site sees ~266 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves comfortable headroom for succession planting.
Growing degree days
Horehound needs ~800 GDD (base 50°F) to ripen. The state median runs ~3945 GDD (from PRISM 1991-2020 climate normals), so Arizona'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
Horehound tolerates a wide pH range (pH 4.5-7.5) — 3 units, acid ground through alkaline — so soil acidity is rarely what limits it in Arizona. A soil test is still worth having, but for what else it tells you about this site, not to clear this plant. It will grow across that whole span, but it does best between pH 5.5 and 7 — worth knowing before you decide whether a Arizona soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Arizona 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. Arizona soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Horehound in Arizona — Quick Answer
- Verdict: Generally — Most Areas
- Plant Zones: 3-9 (USDA PLANTS Database)
- State Zones: 5b-10b (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Feb 1 - Apr 2 to Nov 13 - Dec 12 (NOAA Regional Climate Centers ACIS, 1991-2020)
- Days to Maturity: 90 days
What Else to Consider for Horehound in Arizona
Zone compatibility tells you about winter cold survival — but Arizona growers also need to think about:
Extreme heat exceeding 110F stresses most plants
Minimal rainfall requires drip irrigation
Caliche hardpan prevents root penetration without breaking through
What to actually do about these — and the constraints that apply to every Arizona grower, not just horehound — is covered on the Arizona growing guide.
Timing shifts within Arizona
Horehound needs about 90 days of frost-free season to complete its cycle. Even Coconino County — Arizona’s shortest season at 150 frost-free days — clears that by 60 days, so season length isn’t the constraint anywhere in Arizona. What varies is your own parcel.
Across Arizona’s 15 counties the frost-free season runs from 150 days in Coconino County to 345 days in Maricopa County — a spread of 195 days, which is why a single statewide planting date misleads. The median Arizona county sees 266 frost-free days, leaving horehound about 176 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"). Horehound's 90-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Where in Arizona Fits Best
Even within Arizona's zones 5b-10b, county microclimates differ enough to change what thrives. These counties carry the closest zone match for horehound (USDA PHZM 2023):
Pollinator + Wildlife Value
Horehound draws honeybees and native bees (moderate value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, horehound can only work that bloom inside Arizona's frost window — roughly 266 days, opening after the last 28°F freeze (Feb 1 - Apr 2) and closing at the first (Nov 13 - Dec 12), per NOAA Regional Climate Centers ACIS, 1991-2020.
Arizona Cooperative Extension
For Arizona-specific cultivar recommendations, planting calendars, and pest pressure for horehound, the canonical source is University of Arizona Cooperative Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Horehound native to Arizona?
No — the USDA PLANTS Database lists Horehound as introduced rather than native in the Lower 48, so it is not part of Arizona's native flora. It grows here as a garden plant; pairing it with a few Arizona natives keeps local pollinators fed too.
Looking for plants that belong here? The Arizona 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 Horehound in Arizona
When can I plant Horehound in Arizona?
Arizona's last spring hard freeze (28°F) clears between Feb 1 and Apr 2, and the first fall hard freeze lands between Nov 13 and Dec 12 (NOAA Regional Climate Centers ACIS, 1991-2020). No sourced winter-hardiness floor is on record for Horehound, so this page does not state whether it overwinters in Arizona 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 Horehound grown in across Arizona?
Arizona spans USDA hardiness zones 5b-10b (USDA ARS PHZM 2023). Horehound carries a range of zones 3-9, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Arizona site have?
A typical Arizona site sees ~266 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Horehound needs 90+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Horehound native to Arizona?
No — the USDA PLANTS Database lists Horehound as introduced rather than native in the Lower 48, so it is not part of Arizona's native flora. It grows here as a garden plant; pairing it with a few Arizona natives keeps local pollinators fed too.
How should I amend the soil for Horehound in Arizona?
Horehound tolerates pH 4.5-7.5 and well (dry spells) drainage (Growable Ground Plant Database). That is a 3-unit span, acid ground through alkaline, so pH is rarely what limits this plant on a Arizona site — amend for drainage and organic matter first.
Will Horehound actually grow on my specific land in Arizona?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores horehound 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 Arizona
State-level data is a sketch. Your Growable Ground report scores horehound against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Arizona horehound averages can't show:
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