Unlikely — Zone Mismatch
true yam (zones 9-12) does not overlap with Massachusetts's zone range (5a-7b). Growing outdoors is unlikely without significant protection.
2 zones short — what would close it
True Yam is hardy to zone 9, and the warmest ground in Massachusetts is zone 7 — 2 zones short. Planted in open ground it will not survive a Massachusetts winter. To grow it here, grow true yam 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 9-12 (plant) against 5-7 (Massachusetts). Lift modeled by crop_engine.GREENHOUSE_ZONE_MODIFIER_BY_SUBTYPE['earth_sheltered'] (+2.5 zones) via api/fast_sections.py Unlock Engine v2.
True Yam in Massachusetts — the short answer
True Yam in Massachusetts: hardy in zones 9–12, full sun, against a state median of ~206 frost-free days.
- Plant zones
- 9-12
- Manual horticultural correction (source not retained); NC State Extension and Missouri Botanical Garden, with the remaining rows from other published sources or Growable Ground compilation
- Massachusetts zones
- 5a-7b
- USDA PHZM 2023
- Frost window
- Apr 4 - Apr 14 – Oct 24 - Nov 14
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 171 days
- NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze
- Days to maturity
- 270 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.
Massachusetts spans zones 5a-7b, 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.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Massachusetts is not one climate
A single Massachusetts answer averages 14 counties whose growing seasons are 75 days apart — from 171 frost-free days in Berkshire County to 246 in Nantucket County. Which end of that your land sits nearer changes what true yam can finish before the first hard freeze.
The middle half of 14 counties runs 193–226 days, with a median of 205 days — a 75-day span end to end.
Measured across 14 Massachusetts counties. NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze. 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 True Yam Stands in Massachusetts
True Yam is rated for zones 9–12 — a cold floor USDA puts at 20 to 30°F. No Massachusetts 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 Massachusetts winters, not about true yam.
Below the zone 9 floor
14 counties
- Berkshire County · zone 5b
- Franklin County · zone 6a
- Hampshire County · zone 6a
3 of 14 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
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
Massachusetts Has
- USDA Zones: 5a-7b
- Last Hard Freeze (28°F): Apr 4 - Apr 14
- First Hard Freeze (28°F): Oct 24 - Nov 14
- Annual Rainfall: 42-50 inches
- Common Soils: Glacial till, Sandy loam, Rocky loam
Plant Zone Range (zones 9-12)
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 True Yam in Massachusetts
The frost window
Across Massachusetts, the last spring hard freeze (28°F) clears between Apr 4 and Apr 14, and the first fall hard freeze lands between Oct 24 and Nov 14 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 193-day window you can count on — up to 224 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 — FAO ECOCROP puts its killing temperature at 48.2°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.
Days to maturity vs. the window
At 270 days to maturity (Growable Ground Plant Database), even Massachusetts's kindest 224-day season runs short — challenging without season extension. An indoor start plus row cover on both shoulders of the season closes the gap.
Timing tuned to sub-state frost dates — Berkshire 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 true yam does not survive a Massachusetts 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 Massachusetts under protection.
Frost-free days
True Yam wants 220+ frost-free days; a typical Massachusetts site sees ~206 (NOAA Regional Climate Centers ACIS, 1991-2020) — 14 days short of what it needs. A typical Massachusetts season does not carry this crop to harvest outdoors, and a gap that size is not one an earlier sowing date or a faster cultivar closes; growing it here means growing it under cover.
Growing degree days
True Yam needs ~4000 GDD (base 50°F) to ripen. The state median runs ~2506 GDD (from PRISM 1991-2020 climate normals), so Massachusetts's typical season runs short on heat — pick a south-facing site and consider season extension.
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 Massachusetts. 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 Massachusetts soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Massachusetts site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Your land, not the state average
Whether true yam is safe to eat from Massachusetts soil is a block-by-block question, not a town-wide one — 40,795 documented contamination sites mean levels spike on some parcels and not the one next door. True Yam roots to about 59 inches, so it is the top 59 inches under your address that decide what it takes up, so only a test on your address settles it.
Check your parcel → Source: USDA NRCS SSURGO + EPA/state contamination databases.
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. Massachusetts soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Before you plant true yam 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 true yam goes in. What follows is Massachusetts’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 Massachusetts — and how to grow with it.
We checked the federal record across Massachusetts — 40,795 documented sites across 8 of the 9 source types we track.
The most significant on record: 417 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Massachusetts 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 with clean imported soil grow well almost anywhere in the meantime.
Sources Checked
across Massachusetts
Severity Distribution
across Massachusetts
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Massachusetts, Brownfields runs higher than the national average — 23,042 sites across Massachusetts. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Brownfields: Brownfield sites are former commercial or industrial properties where legacy soil contamination (heavy metals, PAHs, petroleum compounds) may persist.
Check EPA brownfield remediation status — many sites have completed cleanup with institutional controls.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What Else to Consider for True Yam in Massachusetts
Zone compatibility tells you about winter cold survival — but Massachusetts growers also need to think about:
Short growing season (120-180 frost-free days) limits warm-season crops
Rocky glacial soils require amendment in many areas
Late spring frosts can damage early plantings through mid-May
Deer pressure is significant in suburban and rural areas
Growing true yam here specifically
True Yam is a root crop whose edible part grows in or against the soil and can take up lead, and Massachusetts carries 40,795 documented contamination sites where legacy fill and old paint push metals up parcel by parcel.
Grow true yam in raised beds of tested clean soil and run a parcel soil-lead test before planting. How to handle it →
What to actually do about these — and the constraints that apply to every Massachusetts grower, not just true yam — is covered on the Massachusetts growing guide.
Timing shifts within Massachusetts
Massachusetts isn't one climate. In Berkshire County, the last hard freeze (28°F) holds until about Apr 29 — roughly 19 days later than the recorded state median — so plant true yam to your county's window, not the statewide date.
True Yam needs about 220 days of frost-free season to complete its cycle. 4 of Massachusetts’s 14 counties give it that outright. The tightest that does is Barnstable County at 226 frost-free days — 6 to spare. Below that line you are transplanting or extending the season, not direct-sowing.
Across Massachusetts’s 14 counties the frost-free season runs from 171 days in Berkshire County to 246 days in Nantucket County — a spread of 75 days, which is why a single statewide planting date misleads. The median Massachusetts county sees 206 frost-free days, which is 14 days short of what true yam needs — so on a typical Massachusetts parcel this is a transplant-or-protect crop, not a direct-sow one.
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.
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 Massachusetts's frost window — roughly 206 days, opening after the last 28°F freeze (Apr 4 - Apr 14) and closing at the first (Oct 24 - Nov 14), per NOAA Regional Climate Centers ACIS, 1991-2020.
Good to Know Before You Plant True Yam
True Yam is listed as toxic to dogs, cats (all) at a mild level (Cornell). Most listed plants only cause brief upset — a raised bed or a fenced corner usually keeps curious pets clear. Worth knowing for placement: in Massachusetts this is a one-season plant and the first hard freeze (Oct 24 - Nov 14) takes it down, so the exposure above is a summer-long one rather than something standing in the bed all year.
Massachusetts Cooperative Extension
For Massachusetts-specific cultivar recommendations, planting calendars, and pest pressure for true yam, the canonical source is UMass Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is True Yam native to Massachusetts?
No — the USDA PLANTS Database lists True Yam as introduced rather than native in the Lower 48, so it is not part of Massachusetts's native flora. It grows here as a garden plant; pairing it with a few Massachusetts natives keeps local pollinators fed too.
Looking for plants that belong here? The Massachusetts 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 Massachusetts
When can I plant True Yam in Massachusetts?
Massachusetts's last spring hard freeze (28°F) clears between Apr 4 and Apr 14, and the first fall hard freeze lands between Oct 24 and Nov 14 (NOAA Regional Climate Centers ACIS, 1991-2020). True Yam is frost-tender — its killing temperature is 48.2°F (FAO ECOCROP — the point where cold damages growing tissue, not a winter-survival floor) — 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 Massachusetts?
True Yam needs 270 days to mature (Growable Ground Plant Database), and even Massachusetts's longest typical season runs 224 days (NOAA Regional Climate Centers ACIS, 1991-2020) — challenging without season extension. An indoor start plus row cover on both season shoulders closes the gap.
What hardiness zone is True Yam grown in across Massachusetts?
Massachusetts spans USDA hardiness zones 5a-7b (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 Massachusetts site have?
A typical Massachusetts site sees ~206 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. In cooler counties like Berkshire, the freeze-free season runs shorter than the state average, so verify your own county's window.
Is True Yam native to Massachusetts?
No — the USDA PLANTS Database lists True Yam as introduced rather than native in the Lower 48, so it is not part of Massachusetts's native flora. It grows here as a garden plant; pairing it with a few Massachusetts natives keeps local pollinators fed too.
How should I amend the soil for True Yam in Massachusetts?
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 Massachusetts site — amend for drainage and organic matter first.
Will True Yam actually grow on my specific land in Massachusetts?
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 Massachusetts
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 Massachusetts true yam averages can't show:
We read public map data around Massachusetts — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Massachusetts true yam average
Explore More
Growing guides for true yam
Explore Massachusetts county by county
Massachusetts carries 14 counties with their own USDA zone — a sample of the growing pages for true yam there:
Where else true yam grows
True Yam's zone band crosses state lines — these are the states closest to Massachusetts 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 Massachusetts
Massachusetts has a growing page for 893 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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