True Yam is 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.
Zones
9-12
pH Range
4.8-8.5
Sun
Full Sun
Days to Maturity
270
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What True Yam is
True Yam reaches around ten feet at maturity. It's also deer-resistant.
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 and a growing season of at least 220 frost-free days, which is why climate matters as much as soil.
USDA Zones
9-12
USDA PHZM 2023
Soil pH
4.8 - 8.5
USDA PLANTS Database
Sun
Full Sun
Growable Ground plant catalog
Drainage
well (dry spells)
Growable Ground plant catalog
Frost Tolerance
57.2°F
The lowest temperature it shrugs off — below this, expect damage without cover.
Growable Ground plant catalog
Days to Maturity
270 days
Growable Ground plant catalog
GDD Required
4000+
Growing degree-days of accumulated warmth it needs to mature — humid summers reach this faster than cool coastal ones.
Growable Ground plant catalog
Mature Height
10 ft
Growable Ground plant catalog
Frost-Free Days
220+
The frost-free stretch it needs start to finish — short-season areas may need an indoor head start.
Growable Ground plant catalog
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. A 2–3 inch mulch layer holds moisture without waterlogging.
Harvest at maturity
True Yam is ready about 270 days after sowing (University Extension production guides). Pull while roots are young and tender — sweeter than oversized ones.
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.
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 9 federal source types across roughly 1.8M 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.
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.
Zones 9–12·Where True Yam growsOpen map →
On USDA hardiness-zone overlap, True Yam can grow in these states:
See if True Yam will thrive on your land
Zone averages are a start. Your exact soil pH, drainage, sun exposure, and frost dates shape whether true yam actually takes — we score it against the real 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.
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Frequently Asked Questions
Can I grow True Yam in my zone?
True Yam grows in USDA hardiness zones 9 through 12 (USDA PHZM 2023). 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 (University Extension production guides). 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, leaving enough of the season for its 220-day frost-free need. 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. 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 actual 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.
Is True Yam safe for pets?
True Yam is toxic to pets (dogs,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.)