Unlikely — Zone Mismatch
French lavender (zones 8-9) does not overlap with Iowa's zone range (4b-6a). Growing outdoors is unlikely without significant protection.
2 zones short — what would close it
French Lavender is hardy to zone 8, and the warmest ground in Iowa is zone 6 — 2 zones short. Planted in open ground it will not survive a Iowa winter. To grow it here, grow french lavender under glass — a greenhouse is the only lift this wide the engine models.
A greenhouse is the lift this needs. How a greenhouse changes what you can grow →
Zone math from 8-9 (plant) against 4-6 (Iowa). Lift modeled by crop_engine Sprint 20B effective_zone_modifier (+2 zones) via api/fast_sections.py Unlock Engine v2.
Your yard isn't the whole zone.
Iowa spans zones 4b-6a, 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 french lavender against your parcel's actual hardiness, soil, and sun.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Zone Comparison
French Lavender Needs
- USDA Zones: 8-9
- Frost-Free Days: 180+
- Sun: Full Sun
- Mature size: 2 ft tall
- Picking window: ~30 days of harvest
- Drought tolerance: High
Iowa Has
- USDA Zones: 4b-6a
- Last Hard Freeze (28°F): Apr 10 - Apr 17
- First Hard Freeze (28°F): Oct 18 - Oct 23
- Annual Rainfall: 26-36 inches
- Common Soils: Prairie loess, Silt loam, Clay loam
Plant Zone Range (zones 8-9)
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 French Lavender in Iowa
The frost window
Across Iowa, the last spring hard freeze (28°F) clears between Apr 10 and Apr 17, and the first fall hard freeze lands between Oct 18 and Oct 23 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 184-day window you can count on — up to 196 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 french lavender goes out, not when it starts. It is sown under cover about 10 weeks ahead, so counting back from Iowa's late-side last freeze of Apr 17 is what fixes your sowing date — and a yard that clears frost earlier than the state's late date starts earlier still.
Winter standing
French Lavender overwinters from USDA zone 8 and warmer (NC State Extension Gardener Plant Toolbox; Missouri Botanical Garden Plant Finder), and Iowa runs as cold as zone 4, so it does not survive winter in the ground here. It is a woody plant rather than a crop you resow each spring, so neither a fall establishment date nor a harvest countdown describes it in Iowa — which is why this page gives neither. What it needs here is a way through winter, not a planting date.
Timing tuned to sub-state frost dates — Howard 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 french lavender does not survive a Iowa winter in the ground. The season figures below measure a different question — whether it could finish a season here at all — and they only bear on Iowa under protection.
Frost-free days
French Lavender wants 180+ frost-free days; a typical Iowa site sees ~189 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves a tight window — use transplants and pick early-maturing cultivars.
Growing degree days
French Lavender needs ~1200 GDD (base 50°F) to ripen. The state median runs ~2730 GDD (from PRISM 1991-2020 climate normals), so Iowa'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
French Lavender likes near-neutral soil (pH 5.8-8.3). That's the common-ground band across Iowa's prairie loess and silt loam — a soil test confirms it for your site. It will grow across that whole span, but it does best between pH 6.5 and 7.5 — worth knowing before you decide whether a Iowa soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells), excessive (dry/moderately dry). If your Iowa site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Your land, not the state average
SSURGO maps about 42.9% of Iowa as poorly or somewhat-poorly drained, and the class flips parcel to parcel. French Lavender tolerates drought well, so wet feet — not dry spells — is its real risk here — your soil map unit, not the state average, is the real answer.
Check your parcel → Source: USDA NRCS SSURGO.
Plant pH and drainage requirements from USDA PLANTS Database. Iowa soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
French Lavender in Iowa — Quick Answer
- Verdict: Unlikely — Zone Mismatch
- Plant Zones: 8-9 (USDA PLANTS Database)
- State Zones: 4b-6a (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Apr 10 - Apr 17 to Oct 18 - Oct 23 (NOAA Regional Climate Centers ACIS, 1991-2020)
- Days to Maturity: 90 days
What Else to Consider for French Lavender in Iowa
Zone compatibility tells you about winter cold survival — but Iowa growers also need to think about:
Cold winters reaching -20F or below
Variable spring weather delays planting
Wind exposure on open prairies desiccates plants
Growing french lavender here specifically
French Lavender likes pH 5.8–8.3 and takes cold to about 44°F, yet neither saves it from wet feet — SSURGO maps about 42.9% of Iowa poorly-drained, where its crown sit and rot.
Set french lavender high on bermed, grit-amended ground so winter and storm water drain away from the crown. How to handle it →
What to actually do about these — and the constraints that apply to every Iowa grower, not just french lavender — is covered on the Iowa growing guide.
Timing shifts within Iowa
Iowa isn't one climate. In Howard County, the last hard freeze (28°F) holds until about Apr 24 — roughly 10 days later than the recorded state median — so plant french lavender to your county's window, not the statewide date.
French Lavender needs about 180 days of frost-free season to complete its cycle. 90 of Iowa’s 99 counties give it that outright. The tightest that does is Plymouth County at 180 frost-free days — 0 to spare. Below that line you are transplanting or extending the season, not direct-sowing.
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"). French Lavender's 180-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Pollinator + Wildlife Value
French Lavender draws honeybees, native bees, and butterflies (high value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, french lavender can only work that bloom inside Iowa's frost window — roughly 189 days, opening after the last 28°F freeze (Apr 10 - Apr 17) and closing at the first (Oct 18 - Oct 23), per NOAA Regional Climate Centers ACIS, 1991-2020.
Good to Know Before You Plant French Lavender
French Lavender is listed as toxic to dogs, cats (all) at a mild level (ASPCA). Most listed plants only cause brief upset — a raised bed or a fenced corner usually keeps curious pets clear. Worth knowing for placement: french lavender is woody and hardy only from zone 8, against a Iowa low of zone 4, so it is overwintered under cover here rather than left standing outside — which is where it will be in reach.
Recommended French Lavender Varieties for Iowa
Iowa publishes no state variety trial for french lavender, so we won't invent a "best for Iowa" list. Choose types rated to your USDA hardiness zone (4b-6a), and confirm winter survival and drainage against your own parcel.
Iowa Cooperative Extension
For Iowa-specific cultivar recommendations, planting calendars, and pest pressure for french lavender, the canonical source is Iowa State University Extension and Outreach. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is French Lavender native to Iowa?
No — the USDA PLANTS Database lists French Lavender as introduced rather than native in the Lower 48, so it is not part of Iowa's native flora. It grows here as a garden plant; pairing it with a few Iowa natives keeps local pollinators fed too.
Looking for plants that belong here? The Iowa 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 French Lavender in Iowa
When can I plant French Lavender in Iowa?
Iowa's last spring hard freeze (28°F) clears between Apr 10 and Apr 17, and the first fall hard freeze lands between Oct 18 and Oct 23 (NOAA Regional Climate Centers ACIS, 1991-2020). French Lavender overwinters only from USDA zone 8 and warmer, and Iowa runs as cold as zone 4, so it does not survive winter in the ground here — the question for Iowa growers is how to carry it through winter under cover, not which week to plant it.
What hardiness zone is French Lavender grown in across Iowa?
Iowa spans USDA hardiness zones 4b-6a (USDA ARS PHZM 2023). French Lavender carries a range of zones 8-9, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Iowa site have?
A typical Iowa site sees ~189 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). French Lavender needs 180+ 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 Howard, the freeze-free season runs shorter than the state average, so verify your own county's window.
Is French Lavender native to Iowa?
No — the USDA PLANTS Database lists French Lavender as introduced rather than native in the Lower 48, so it is not part of Iowa's native flora. It grows here as a garden plant; pairing it with a few Iowa natives keeps local pollinators fed too.
How should I amend the soil for French Lavender in Iowa?
French Lavender prefers pH 5.8-8.3 and well (dry spells), excessive (dry/moderately dry) drainage (FAO ECOCROP). That sits in the common-ground band across Iowa soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will French Lavender actually grow on my specific land in Iowa?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores french lavender 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 Iowa
State-level data is a sketch. Your Growable Ground report scores french lavender against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Iowa french lavender averages can't show:
We read public map data around Iowa — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Iowa french lavender average
Explore More
Growing guides for french lavender
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
Last updated: