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.
Cast Iron Plant — the short answer
Cast Iron Plant: grown in zones 7–11, shade, pH 5.5–7.
- USDA zones
- 7–11
- NC State Extension Gardener Plant Toolbox
- Soil pH
- 5.5–7
- We haven't confirmed this against a published source yet.
- Sun
- Shade
- NC State Extension Gardener Plant Toolbox
- Frost-kill temp (growing season)
- 0°F
- We haven't confirmed this against a published source yet.
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 Cast Iron Plant on your exact land.
Zone averages can't see the slope, soil, frost, and sun that decide whether cast iron plant actually takes — and those shift from one yard to the next. Enter your address and we'll score cast iron plant against your land's real conditions.
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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.
Mature height, bloom period, flower colour and container suitability: We haven't confirmed this against a published source yet.
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.
USDA Zones
7-11
NC State Extension Gardener Plant Toolbox
Soil pH
5.5 - 7
We haven't confirmed this against a published source yet.
Sun
Shade
NC State Extension Gardener Plant Toolbox
Drainage
well (dry spells)
We haven't confirmed this against a published source yet.
Frost Kill Temperature
0°F
Where cold starts killing growing tissue. Not a winter-survival floor — a dormant perennial takes far colder, which its hardiness zone answers.
We haven't confirmed this against a published source yet.
Mature Height
2 ft
We haven't confirmed this against a published source yet.
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. We haven't confirmed this against a published source yet.
Match the soil
Cast Iron Plant prefers pH 5.5 to 7. We haven't confirmed this against a published source yet. A quick soil test from your local Extension lab tells you whether to add lime or sulfur to land in band.
Water while it roots in
Water deeply while cast iron plant establishes, letting the soil dry between soakings; once its roots are in, it rides out dry spells on its own.
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.
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.
A USDA zone is a 10°F band of average annual extreme winter minimum, so zones 7–11 spans average winter lows from 0°F to 50°F (USDA PHZM 2023). Across the 50 states and DC, that band covers 7 outright and splits 34 more down the middle — and which side of that line your land sits on changes the answer.
Zones 7–11·Where Cast Iron Plant 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 Cast Iron Plant stands, state by state
Cast Iron Plant is rated for zones 7–11 — a cold floor USDA puts at 0 to 10°F. Across the 50 states and DC, 7 sit fully inside that band, the line runs through 34 more, and 10 sit outside it — and inside every split state, the same line runs on at county grain.
Fully inside zones 7–11
7 states
- Alabama · zones 7b-9b
- Delaware · zones 7a-8a
- District of Columbia · zones 7b-8a
3 of 7 shown
The line runs through
34 states
3 of 34 shown
Cast Iron Plant’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.
Outside zones 7–11
10 states
- Minnesota · zones 3a-5a
- Montana · zones 3a-6b
- New Hampshire · zones 3b-6b
3 of 10 shown
Winter cold is the limit here — the same plant often works in a container that comes under cover. Each link is that state’s own growing hub.
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 Cast Iron Plant
Growing guides for cast iron plant
Related plants in houseplant/patio
Good to know
Listed as non-toxic to dogs and cats by a source we can't cite. We haven't confirmed this against a published source yet.
Cast Iron Plant isn't classified as a notable pollinator plant in our data — pair it with high-value bloomers nearby to feed bees.
Your land is one point inside Cast Iron Plant'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 Cast Iron Plant will thrive on your land
Zone averages are a start. Your soil pH, drainage, sun exposure, and frost dates shape whether cast iron plant 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 Cast Iron Plant
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 Cast Iron Plant in my zone?
Cast Iron Plant grows in USDA hardiness zones 7 through 11 (NC State Extension Gardener Plant Toolbox). 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. 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. We haven't confirmed this against a published source yet. 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. We haven't confirmed this against a published source yet. Your report scores your parcel's mapped 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.
Keep exploring Cast Iron Plant
Cast Iron Plant state by state
Every state cast iron plant's zone reaches — 13 link straight to that state's cast iron plant growing page; the rest open the state's full growing guide.