Conditional — Some Areas
true yam (zones 9-12) reaches only part of Mississippi (7b-9b): zone 9 are in range, so where you are in the state decides it.
Your yard isn't the whole zone.
Mississippi spans zones 7b-9b, but your yard has its own microclimate — slope, trees, and low spots shift frost and sun across a single parcel. Enter your address and we'll score true yam against your land's actual soil, sun, and frost.
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Zone Comparison
True Yam Needs
- USDA Zones: 9-12
- Frost-Free Days: 220+
- Sun: Full Sun
- Mature size: 10 ft tall
- Picking window: ~30 days of harvest
- Drought tolerance: Medium
Mississippi Has
- USDA Zones: 7b-9b
- Last Hard Freeze (28°F): Feb 17 - Mar 3
- First Hard Freeze (28°F): Nov 21 - Nov 30
- Annual Rainfall: 50-65 inches
- Common Soils: Loess, Alluvial clay, Sandy loam
Plant Zone Range (zones 9-12)
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 True Yam in Mississippi
The frost window
Across Mississippi, the last spring hard freeze (28°F) clears between Feb 17 and Mar 3, and the first fall hard freeze lands between Nov 21 and Nov 30 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 263-day window you can count on — up to 286 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
True Yam is frost-tender — its listed minimum temperature is 57.2°F (USDA PLANTS Database) — 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.
Days to maturity vs. the window
At 270 days to maturity (USDA PLANTS Database), the fit is tight: Mississippi's dependable window runs 263 days. Starting seeds indoors and transplanting at the front of the window banks the difference.
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 true yam survives winter in part of Mississippi, not across all of it. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
True Yam wants 220+ frost-free days; a typical Mississippi site sees ~273 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves a workable window — start indoors to bank time.
Growing degree days
True Yam needs ~4000 GDD (base 50°F) to ripen. The state median runs ~5404 GDD (from PRISM 1991-2020 climate normals), so Mississippi'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
True Yam tolerates a wide pH range (pH 4.8-8.5) — 3.7 units, acid ground through alkaline — so soil acidity is rarely what limits it in Mississippi. 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 6.5 — worth knowing before you decide whether a Mississippi soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Mississippi 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. Mississippi soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
True Yam in Mississippi — Quick Answer
- Verdict: Conditional — Some Areas
- Plant Zones: 9-12 (USDA PLANTS Database)
- State Zones: 7b-9b (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Feb 17 - Mar 3 to Nov 21 - Nov 30 (NOAA Regional Climate Centers ACIS, 1991-2020)
- Days to Maturity: 270 days
What Else to Consider for True Yam in Mississippi
Zone compatibility tells you about winter cold survival — but Mississippi growers also need to think about:
Extreme summer heat and humidity
Heavy alluvial clay in the Delta region
Frequent severe storms and flooding
What to actually do about these — and the constraints that apply to every Mississippi grower, not just true yam — is covered on the Mississippi growing guide.
Timing shifts within Mississippi
True Yam needs about 220 days of frost-free season to complete its cycle. Even Tishomingo County — Mississippi’s shortest season at 232 frost-free days — clears that by 12 days, so season length isn’t the constraint anywhere in Mississippi. What varies is your own parcel.
Across Mississippi’s 82 counties the frost-free season runs from 232 days in Tishomingo County to 309 days in Harrison County — a spread of 77 days, which is why a single statewide planting date misleads. The median Mississippi county sees 273 frost-free days, leaving true yam about 53 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"). True Yam's 220-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Where in Mississippi Fits Best
Even within Mississippi's zones 7b-9b, county microclimates differ enough to change what thrives. These counties carry the closest zone match for true yam (USDA PHZM 2023):
Pollinator + Wildlife Value
True Yam draws native bees (low value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, true yam can only work that bloom inside Mississippi's frost window — roughly 273 days, opening after the last 28°F freeze (Feb 17 - Mar 3) and closing at the first (Nov 21 - Nov 30), per NOAA Regional Climate Centers ACIS, 1991-2020.
Mississippi Cooperative Extension
For Mississippi-specific cultivar recommendations, planting calendars, and pest pressure for true yam, the canonical source is Mississippi State University Extension Service. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is True Yam native to Mississippi?
No — the USDA PLANTS Database lists True Yam as introduced rather than native in the Lower 48, so it is not part of Mississippi's native flora. It grows here as a garden plant; pairing it with a few Mississippi natives keeps local pollinators fed too.
Looking for plants that belong here? The Mississippi 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 True Yam in Mississippi
When can I plant True Yam in Mississippi?
Mississippi's last spring hard freeze (28°F) clears between Feb 17 and Mar 3, and the first fall hard freeze lands between Nov 21 and Nov 30 (NOAA Regional Climate Centers ACIS, 1991-2020). True Yam is frost-tender — its listed minimum temperature is 57.2°F (USDA PLANTS Database) — so wait two to three weeks past your site's last hard freeze, when light frost has also stopped, before planting out.
Can True Yam mature before first frost in Mississippi?
It's close: True Yam needs 270 days to mature (USDA PLANTS Database) against Mississippi's 263-day dependable window (NOAA Regional Climate Centers ACIS, 1991-2020). Start seeds indoors and transplant once the last hard freeze has passed to bank the missing days.
What hardiness zone is True Yam grown in across Mississippi?
Mississippi spans USDA hardiness zones 7b-9b (USDA ARS PHZM 2023). True Yam carries a range of zones 9-12, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Mississippi site have?
A typical Mississippi site sees ~273 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). True Yam needs 220+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is True Yam native to Mississippi?
No — the USDA PLANTS Database lists True Yam as introduced rather than native in the Lower 48, so it is not part of Mississippi's native flora. It grows here as a garden plant; pairing it with a few Mississippi natives keeps local pollinators fed too.
How should I amend the soil for True Yam in Mississippi?
True Yam tolerates pH 4.8-8.5 and well (dry spells) drainage (FAO ECOCROP). That is a 3.7-unit span, acid ground through alkaline, so pH is rarely what limits this plant on a Mississippi site — amend for drainage and organic matter first.
Will True Yam actually grow on my specific land in Mississippi?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores true yam 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 Mississippi
State-level data is a sketch. Your Growable Ground report scores true yam against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Mississippi true yam averages can't show:
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