Cast Iron Plant is grown for its foliage and the structure it brings to a planting. It's hardy across USDA zones 7 through 11, shrugs off deer, shrugs off dry spells, and grows just as well in a container as in the ground.
Zones
7-11
pH Range
5.5-7
Sun
Shade
Days to Maturity
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Score Cast Iron Plant on your exact land.
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See Cast Iron Plant
What Cast Iron Plant is
Cast Iron Plant grows as a perennial and reaches around two feet at maturity. It blooms purple in spring. It's also deer-resistant and well suited to containers.
How to grow Cast Iron Plant
Cast Iron Plant grows in USDA zones 7 through 11. Cast Iron Plant does best in shade — at least 2 hours of direct sun a day — and soil from pH 5.5 to 7, on well-drained ground. It needs a growing season of at least 120 frost-free days, which is why climate matters as much as soil.
USDA Zones
7-11
USDA PHZM 2023
Soil pH
5.5 - 7
USDA PLANTS Database
Sun
Shade
Growable Ground plant catalog
Drainage
well (dry spells)
Growable Ground plant catalog
Mature Height
2 ft
Growable Ground plant catalog
Frost-Free Days
120+
The frost-free stretch it needs start to finish — short-season areas may need an indoor head start.
Growable Ground plant catalog
Start the season right
Plant cast iron plant in shade with at least 2 hours of direct sun, once the soil has warmed and frost risk has passed.
Match the soil
Cast Iron Plant prefers pH 5.5 to 7 (Growable Ground Plant Database). 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.
Keep it in good form
Prune cast iron plant to shape as it grows; the reward is its foliage and structure, not a harvest, so steady upkeep is the whole job.
Good to know
Good news for pet owners — cast iron plant isn't known to be toxic to dogs or cats. (Source: ASPCA.)
Cast Iron Plant isn't classified as a notable pollinator plant in our data — pair it with high-value bloomers nearby to feed bees.
Where Cast Iron Plant thrives
Cast Iron Plant is hardy across USDA zones 7 through 11. 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 7–11·Where Cast Iron Plant growsOpen map →
On USDA hardiness-zone overlap, Cast Iron Plant can grow in these states:
See if Cast Iron Plant will thrive on your land
Zone averages are a start. Your exact soil pH, drainage, sun exposure, and frost dates shape whether cast iron plant 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 Cast Iron Plant in my zone?
Cast Iron Plant grows in USDA hardiness zones 7 through 11 (USDA PHZM 2023). Zone is one factor — soil pH, drainage, and frost dates on your specific parcel also shape whether it takes.
When should you plant Cast Iron Plant?
Most growers plant cast iron plant after the last spring frost, once the soil has warmed, leaving enough of the season for its 120-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 Cast Iron Plant need?
Cast Iron Plant is shade-tolerant — it gets by on as little as 2 hours of direct sun, so it earns a place most vegetables can't use. A north-facing strip or the ground under a leafy canopy is right where it belongs. A Growable Ground report shows which corners of your land stay shaded through the day, turning those dim spots into planting spots.
What soil does Cast Iron Plant need?
Cast Iron Plant prefers soil pH 5.5 to 7, on well-drained ground (Growable Ground Plant Database). Your report scores your parcel's actual soil against that using USDA SSURGO data.
Does Cast Iron Plant attract pollinators?
Cast Iron Plant isn't classified as a notable pollinator plant in our data. Pairing it with high-value bloomers nearby keeps bees and butterflies fed.
Is Cast Iron Plant safe for pets?
Cast Iron Plant is not known to be toxic to dogs or cats based on available data. Always supervise pets around new plantings. (Source: ASPCA.)