In Florida, the FDACS Florida Noxious Weed Index lists True Yam (Dioscorea alata) as a prohibited plant, and UF/IFAS does not recommend it. Check your state's rules before you plant it.
True Yam is a perennial grown for its root, ready to pull about 270 days after sowing. It's hardy across USDA zones 9 through 12 and stands up to deer. Its flowers are a modest draw for native bees, even though the root is the prize. It roots deep, which helps it reach moisture in a dry spell and open up tight soil as it establishes.
True Yam — the short answer
True Yam: grown in zones 9–12, full sun, pH 4.8–8.5, about 270 days to maturity.
- USDA zones
- 9–12
- Not verified
- Soil pH
- 4.8–8.5
- FAO ECOCROP
- Sun
- Full Sun
- Converted from FAO ECOCROP
- Days to Maturity
- 270 days
- We haven't confirmed this against a published source yet.
- Frost-kill temp (growing season)
- 48.2°F
- FAO ECOCROP
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS and university Extension sources — each tile names its own row's source, because per-field provenance varies.
Score True Yam on your exact land.
Zone averages can't see the slope, soil, frost, and sun that decide whether true yam actually takes — and those shift from one yard to the next. Enter your address and we'll score true yam against your land's real conditions.
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What True Yam is
True Yam grows as a perennial and reaches around ten feet at maturity. It's also deer-resistant.
Life cycle, mature height and deer resistance: We haven't confirmed this against a published source yet.
How to grow True Yam
True Yam grows in USDA zones 9 through 12 and is ready to harvest about 270 days after planting. True Yam does best in full sun — at least 6 hours of direct sun a day — and soil from pH 4.8 to 8.5, on well-drained ground. It needs around 4,000 growing degree days to mature, which is why climate matters as much as soil.
USDA Zones
9-12
Not verified
Soil pH
4.8 - 8.5
FAO ECOCROP
Sun
Full Sun
Converted from FAO ECOCROP
Drainage
well (dry spells)
FAO ECOCROP
Frost Kill Temperature
48.2°F
Where cold starts killing growing tissue. Not a winter-survival floor — a dormant perennial takes far colder, which its hardiness zone answers.
FAO ECOCROP
Minimum Growing Temperature
57.2°F
Below this it stops growing rather than dies — a pace limit, not a survival limit.
FAO ECOCROP
Days to Maturity
270 days
We haven't confirmed this against a published source yet.
GDD Required
4000+
Growing degree-days of accumulated warmth it needs to mature — humid summers reach this faster than cool coastal ones.
We haven't confirmed this against a published source yet.
Mature Height
10 ft
We haven't confirmed this against a published source yet.
Sow directly
Sow true yam seed straight into the bed — root crops germinate fast and resent transplanting. Give them full sun.
Match the soil
True Yam prefers pH 4.8 to 8.5 (FAO ECOCROP). A quick soil test from your local Extension lab tells you whether to add lime or sulfur to land in band.
Water steadily
Keep the root zone evenly moist through establishment. We haven't confirmed this against a published source yet. A 2–3 inch mulch layer holds moisture without waterlogging.
Harvest at maturity
True Yam is ready about 270 days after sowing. We haven't confirmed this against a published source yet. Pull while roots are young and tender — sweeter than oversized ones.
Where True Yam thrives
True Yam is hardy across USDA zones 9 through 12. Zone is only the starting point, though: the soil pH, drainage, and frost dates on your specific land decide how well it actually does.
A USDA zone is a 10°F band of average annual extreme winter minimum, so zones 9–12 spans average winter lows from 20°F to 60°F (USDA PHZM 2023). Across the 50 states and DC, that band covers none outright but splits 17 down the middle — and which side of that line your land sits on changes the answer.
Zones 9–12·Where True Yam growsOpen map →
This map is derived from the USDA ARS / PRISM Plant Hardiness Zone Map (2023) and is not the official USDA Plant Hardiness Zone Map.
Where True Yam stands, state by state
True Yam is rated for zones 9–12 — a cold floor USDA puts at 20 to 30°F. Across the 50 states and DC, 0 sit fully inside that band, the line runs through 17 more, and 34 sit outside it — and inside every split state, the same line runs on at county grain.
The line runs through
17 states
- Alaska · zones 1a-9a
- California · zones 4b-11a
- Nevada · zones 4a-10a
3 of 17 shown
True Yam’s band covers part of each of these states — which side of the line your county sits on changes the answer, and each state page draws it.
State zone extents: USDA Plant Hardiness Zone Map (PHZM) 2023. A zone is a 10°F band of average annual extreme minimum temperature, so a state that splits the band contains the boundary — its own page draws the county line, and a parcel report resolves which side your land sits on.
What grows around True Yam
Growing guides for true yam
Related plants in vegetable
Good to know
One caution for pet owners — true yam is toxic to dogs and cats (mild severity). Keep it out of reach, and call ASPCA Animal Poison Control at (888) 426-4435 in an emergency. (Source: Cornell Poisonous Plants Database.)
True Yam offers low value to bees and other pollinators. We haven't confirmed this against a published source yet.
Before you harvest true yam, know your soil
Anything you grow to eat takes up what's in the ground it grows in, so it's worth knowing what's documented near you before you plant true yam for food. Our free screen reads 8 federal source types across roughly 950K indexed sites and shows which sit near your address and which way they drain. It's a screening estimate from public records and proximity — not a soil test — so a nearby record means a soil test is worth it, not that your soil is unsafe.
Your land is one point inside True Yam's range
This page resolves to the species. Your state page draws the county line, and a report reads the parcel — the soil pH, drainage, sun, and frost dates on your exact ground, which no species average can see.
See if True Yam will thrive on your land
Zone averages are a start. Your soil pH, drainage, sun exposure, and frost dates shape whether true yam actually takes. We score it against the mapped and modelled conditions at your address.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources analyzed in seconds
How we know this about True Yam
The figures above are cited per row, not per site: the pH band names this plant’s own source column, the three temperature figures each carry their own, and days-to-maturity cites the publication that actually lists it. All of it comes from the Growable Ground Plant Database — a compilation over FAO ECOCROP, USDA PLANTS, and university Extension sources, published openly with per-field provenance.
Grounded inUSDA PLANTS Database
Frequently asked questions
Can I grow True Yam in my zone?
True Yam grows in USDA hardiness zones 9 through 12. Zone is one factor — soil pH, drainage, and frost dates on your specific parcel also shape whether it takes.
How long does True Yam take to grow?
True Yam is ready to harvest about 270 days after planting. We haven't confirmed this against a published source yet. Your local frost dates and soil temperature move that window earlier or later.
When should you plant True Yam?
Most growers plant true yam after the last spring frost, once the soil has warmed. Your local frost dates set the exact window — a Growable Ground report reads them for your address.
How much sun does True Yam need?
True Yam needs full sun — a spot that catches at least 6 hours of direct summer sun a day. We haven't confirmed this against a published source yet. In more shade it still grows, but usually gives a smaller, later crop. The catch is that a yard rarely gets even light everywhere — a fence, the house, or one tall tree can quietly take those hours. A Growable Ground report reads the real sun-hours across your land, canopy and buildings included, so you can pick the brightest bed before you plant.
What soil does True Yam need?
True Yam prefers soil pH 4.8 to 8.5, on well-drained ground (FAO ECOCROP). Your report scores your parcel's mapped soil against that using USDA SSURGO data.
Does True Yam attract pollinators?
Yes — true yam's flowers are a modest nectar source for native bees. We haven't confirmed this against a published source yet.
Is True Yam safe for pets?
True Yam is toxic to dogs and cats with mild severity. Keep it out of reach, and call ASPCA Animal Poison Control at (888) 426-4435 in an emergency. (Source: Cornell Poisonous Plants Database.)
Keep exploring True Yam
True Yam state by state
Every state true yam's zone reaches — 7 link straight to that state's true yam growing page; the rest open the state's full growing guide.