Unlikely — Zone Mismatch
marjoram (zones 9-10) does not overlap with Illinois's zone range (5a-7b). Growing outdoors is unlikely without significant protection.
2 zones short — what would close it
Marjoram is hardy to zone 9, and the warmest ground in Illinois is zone 7 — 2 zones short. Planted in open ground it will not survive a Illinois winter. To grow it here, grow marjoram in an earth-sheltered greenhouse — its modeled 2.5-zone lift covers this gap.
An earth-sheltered greenhouse is the lift this needs. How a greenhouse changes what you can grow →
Zone math from 9-10 (plant) against 5-7 (Illinois). Lift modeled by crop_engine.GREENHOUSE_ZONE_MODIFIER_BY_SUBTYPE['earth_sheltered'] (+2.5 zones) via api/fast_sections.py Unlock Engine v2.
Marjoram in Illinois — the short answer
Marjoram in Illinois: hardy in zones 9–10, full sun.
- Plant zones
- 9-10
- NC State Extension Gardener Plant Toolbox
- Illinois zones
- 5a-7b
- USDA PHZM 2023
- Frost window
- Mar 29 - Apr 8 – Oct 28 - Nov 5
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 177 days
- NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze
- Days to maturity
- 70 days
- Growable Ground Plant Database
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS and university Extension sources — per-field provenance varies and is published with the dataset.
Your yard isn't the whole zone.
Illinois spans zones 5a-7b, 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 marjoram 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 parcel report in seconds — read in full free for your first 14 days
Illinois is not one climate
Illinois’s winter-low ladder runs across 102 counties, from zone 5 in Carroll County to zone 7 in Williamson County. That is 20°F between the two counties’ average coldest night — the difference between marjoram overwintering in the ground and coming under cover.
The middle half of 102 counties runs 5.5–6.5 zones, with a median of 6 zones — a 2-zone span end to end.
Measured across 102 Illinois counties. USDA PHZM 2023, per county. Quartiles are order statistics — every figure shown is a value a real county recorded, not an interpolation. Your own site sits somewhere inside this range; a parcel report resolves where.
Where Marjoram Stands in Illinois
Marjoram is rated for zones 9–10 — a cold floor USDA puts at 20 to 30°F. No Illinois county sits inside it, so in open ground this is a grown-under-cover plant here rather than a bed plant — which is a statement about Illinois winters, not about marjoram.
Below the zone 9 floor
102 counties
- Carroll County · zone 5a
- Jo Daviess County · zone 5a
- Stephenson County · zone 5a
3 of 102 shown
Winter cold is the limit here — the same plant works in a container that comes under cover.
County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. A zone is a 10°F band of average annual extreme minimum temperature, so the floor above is the band the plant's rating denotes, not a single measured kill point. Slope, shelter and cold-air drainage routinely move a site half a zone either way from its county figure — which is the part only your address resolves.
Zone Comparison
Marjoram Needs
- USDA Zones: 9-10
- Sun: Full Sun
- Mature size: 1.5 ft tallWe haven't confirmed this against a published source yet.
- Picking window: ~90 days of harvestWe haven't confirmed this against a published source yet.
- Drought tolerance: MediumWe haven't confirmed this against a published source yet.
Illinois Has
- USDA Zones: 5a-7b
- Last Hard Freeze (28°F): Mar 29 - Apr 8
- First Hard Freeze (28°F): Oct 28 - Nov 5
- Annual Rainfall: 34-48 inches
- Common Soils: Prairie loam, Silt loam, Clay loam
Plant Zone Range (zones 9-10)
Preferred Soil pH
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS, and university Extension sources — per-field provenance varies and is published with the dataset. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Marjoram in Illinois
The frost window
Across Illinois, the last spring hard freeze (28°F) clears between Mar 29 and Apr 8, and the first fall hard freeze lands between Oct 28 and Nov 5 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 203-day window you can count on — up to 221 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.
Frost tenderness
Marjoram is frost-tender — FAO ECOCROP puts its killing temperature at 32°F — so set plants out two to three weeks PAST your local last hard freeze, not on it and not on the state's earliest date. The 28°F marker above is when killing freezes stop, not when light frost does. That is the point where cold damages growing tissue, not a winter-survival floor — an established perennial comes through far colder while dormant, which is what its hardiness zone tells you.
When to start the seed
Those dates are when marjoram goes out, not when it starts. It is sown under cover about 6 weeks ahead, so counting back from Illinois's late-side last freeze of Apr 8 is what fixes your sowing date — and a yard that clears frost earlier than the state's late date starts earlier still.
Grown as an annual here
Marjoram is a true perennial in its home range — it overwinters from USDA zone 9 and warmer (NC State Extension Gardener Plant Toolbox) — but Illinois runs as cold as zone 5, so it is killed back each winter and replanted each spring. Treat it on the season schedule above, not as a permanent planting: there is no fall establishment window for it here.
Timing tuned to sub-state frost dates — Jo Daviess County, not the statewide average.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: Growable Ground Plant Database — frost-free days from FAO ECOCROP, days to harvest from university Extension production guides, and growing-degree-day and chill-hour minimums that are compilation estimates rather than published figures. 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 marjoram does not survive a Illinois 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 Illinois under protection.
Growing degree days
Marjoram needs ~1200 GDD (base 50°F) to ripen. We haven't confirmed this against a published source yet. The state median runs ~3352 GDD (from PRISM 1991-2020 climate normals), so Illinois'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
Marjoram tolerates a wide pH range (pH 4.9-8.7) — 3.8 units, acid ground through alkaline — so soil acidity is rarely what limits it in Illinois. 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 Illinois soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Illinois site is heavier clay or sits in a low spot, a raised bed lifts the roots above wet ground, or work in compost.
Your land, not the state average
SSURGO maps about 52.0% of Illinois as poorly or somewhat-poorly drained, and the class flips parcel to parcel. Marjoram sits mid-range for drought tolerance, so either extreme can cost you — your soil map unit, not the state average, is the real answer.
Check your parcel → Source: USDA NRCS SSURGO.
Plant pH requirements: FAO ECOCROP and USDA PLANTS, with the remaining rows from other published sources or Growable Ground compilation. Drainage: FAO ECOCROP, with the remaining rows from other published sources or Growable Ground compilation. Illinois soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Before you plant marjoram for food
Anything you grow to eat takes up what is in the ground it grows in, so what is on record near you is worth knowing before marjoram goes in. What follows is Illinois’s documented federal record at state scale — a screening signal, not a soil test, and not a statement about any one lot.
Safe to Grow Here?
What the federal record shows across Illinois — and how to grow with it.
We checked the federal record across Illinois — 35,151 documented sites across 7 of the 8 source types we track.
The most significant on record: 622 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Illinois carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds of imported, lab-tested soil grow well almost anywhere in the meantime.
Sources Checked
across Illinois
Severity Distribution
across Illinois
Highest-Severity Sites
Know Before You Grow
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •TRI facilities report what they release. Check the wind — downwind beds catch more of it.
- •Near a brownfield, a raised bed of imported, lab-tested soil lowers contact with the ground; it does not remove it.
Sources: EPA, USGS — 950K documented sites tracked nationwide across 8 federal source types.
What Else to Consider for Marjoram in Illinois
Zone compatibility tells you about winter cold survival — but Illinois growers also need to think about:
Heavy clay soils in northern IL drain poorly
Extreme temperature swings between summer and winter
Japanese beetles are a major garden pest
Growing marjoram here specifically
Marjoram rates to USDA zones 9–10 and takes frost damage on growing tissue around 32°F (FAO ECOCROP), but cold isn't the risk in Illinois — wet is: with roughly 52.0% of its soils poorly-drained (SSURGO), soggy ground rots the crown.
Give marjoram a raised bed or mounded row with coarse amendment so its crown never sit wet. How to handle it →
What to actually do about these — and the constraints that apply to every Illinois grower, not just marjoram — is covered on the Illinois growing guide.
Timing shifts within Illinois
Illinois isn't one climate. In Jo Daviess County, the last hard freeze (28°F) holds until about Apr 22 — roughly 20 days later than the recorded state median — so plant marjoram to your county's window, not the statewide date.
County last-freeze dates: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F freeze (earlier than the folk 32°F "last frost"). A parcel report resolves your address's own frost dates.
Where in Illinois Marjoram Is Zone-Hardy
Marjoram is rated for USDA zones 9–10. No Illinois county reaches it. Even Williamson County, the state’s mildest winter at zone 7a, sits below the plant’s zone 9 floor — so in open ground this one needs winter protection here, or a container that comes under cover.
Across those 102 counties Illinois’s winter-low ladder runs from zone 5a in Carroll County to zone 7a in Williamson County — 2 USDA zones of spread, which is 20°F between the two counties’ average coldest night of the year. None of that range reaches the band marjoram needs, so here the statewide answer really is the answer.
County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. Marjoram’s zone 9–10 band: NC State Extension Gardener Plant Toolbox. A parcel report resolves your address’s own zone and frost dates rather than its county’s.
Pollinator + Wildlife Value
Marjoram draws honeybees, native bees, and butterflies (high value). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, marjoram can only work that bloom inside Illinois's frost window — roughly 212 days, opening after the last 28°F freeze (Mar 29 - Apr 8) and closing at the first (Oct 28 - Nov 5), per NOAA Regional Climate Centers ACIS, 1991-2020. Pollinator value: We haven't confirmed this against a published source yet.
Good to Know Before You Plant Marjoram
Marjoram is listed as toxic to dogs, cats. (Source: NC State Extension Gardener Plant Toolbox.) Most listed plants only cause brief upset — a raised bed or a fenced corner usually keeps curious pets clear. Worth knowing for placement: in Illinois this is a one-season plant and the first hard freeze (Oct 28 - Nov 5) takes it down, so the exposure above is a summer-long one rather than something standing in the bed all year.
Recommended Marjoram Varieties for Illinois
Illinois publishes no state variety trial for marjoram, so we won't invent a "best for Illinois" list. Choose types rated to your USDA hardiness zone (5a-7b), and confirm winter survival and drainage against your own parcel.
Illinois Cooperative Extension
For Illinois-specific cultivar recommendations, planting calendars, and pest pressure for marjoram, the canonical source is University of Illinois Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Marjoram native to Illinois?
No — the USDA PLANTS Database lists Marjoram as introduced rather than native in the Lower 48, so it is not part of Illinois's native flora. It grows here as a garden plant; pairing it with a few Illinois natives keeps local pollinators fed too.
Looking for plants that belong here? The Illinois growing guide lists plants that USDA PLANTS records growing in Illinois and that Kew and NatureServe Explorer both list in its native range, leaving out any that NatureServe flags as exotic there or that our audit holds.
State records: USDA PLANTS Database state-distribution data (presence, not state-level nativity), accessed 2026-10-19.
Common Questions About Growing Marjoram in Illinois
When can I plant Marjoram in Illinois?
Illinois's last spring hard freeze (28°F) clears between Mar 29 and Apr 8, and the first fall hard freeze lands between Oct 28 and Nov 5 (NOAA Regional Climate Centers ACIS, 1991-2020). Marjoram overwinters only from USDA zone 9 and warmer, and Illinois runs as cold as zone 5, so it is grown as an annual here — plant it after the last hard freeze, two to three weeks later for tender stock, and expect to replant next spring rather than establishing it for the long term.
What hardiness zone is Marjoram grown in across Illinois?
Illinois spans USDA hardiness zones 5a-7b (USDA ARS PHZM 2023). Marjoram is listed for zones 9-10, which do not overlap them, so there is no zone in Illinois where this page can call outdoor growing reliable. A parcel report resolves your own address's zone.
How many frost-free days does a typical Illinois site have?
A typical Illinois site sees ~212 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Marjoram needs 90+ 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 Jo Daviess, the freeze-free season runs shorter than the state average, so verify your own county's window.
Is Marjoram native to Illinois?
No — the USDA PLANTS Database lists Marjoram as introduced rather than native in the Lower 48, so it is not part of Illinois's native flora. It grows here as a garden plant; pairing it with a few Illinois natives keeps local pollinators fed too.
How should I amend the soil for Marjoram in Illinois?
Marjoram tolerates pH 4.9-8.7 and well (dry spells) drainage (FAO ECOCROP). That is a 3.8-unit span, acid ground through alkaline, so pH is rarely what limits this plant on a Illinois site — amend for drainage and organic matter first.
Will Marjoram actually grow on my specific land in Illinois?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores marjoram against your address's mapped soil pH, drainage, sun, and frost-date data drawn from USDA SSURGO, NOAA, and PRISM — not state averages.
Check your specific parcel in Illinois
State-level data is a sketch. Your Growable Ground report scores marjoram against your land's mapped soil, modelled sun, drainage, and frost data — not zone averages.
Three things about your lot that Illinois marjoram averages can't show:
We read public map data around Illinois — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Illinois marjoram average
Explore More
Growing guides for marjoram
Explore Illinois county by county
Illinois carries 102 counties with their own USDA zone — a sample of the growing pages for marjoram there:
Where else marjoram grows
Marjoram's zone band crosses state lines — these are the states closest to Illinois in winter climate where it also has a page, plus the far ends of its range. Each one re-answers the question with that state's own record.
More to grow in Illinois
Illinois has a growing page for 889 plants — a rotating sample of the rest of the shelf.
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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