Ironwood is grown for its foliage and the structure it brings to a planting. It's hardy across USDA zones 10 through 13 and shrugs off dry spells. A nitrogen-fixer, it draws nitrogen from the air and feeds it back to the soil — turn it under or leave the roots in place, and the next planting inherits a richer bed.
Zones
10-13
pH Range
6.8-8.6
Sun
Full Sun
Days to Maturity
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Score Ironwood on your exact land.
Zone averages can't see the slope, soil, frost, and sun that decide whether ironwood actually takes — and those shift from one yard to the next. Enter your address and we'll score ironwood against your land's real conditions.
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What Ironwood is
Ironwood grows as a perennial. It blooms purple in early spring.
How to grow Ironwood
Ironwood grows in USDA zones 10 through 13. Ironwood does best in full sun — at least 6 hours of direct sun a day — and soil from pH 6.8 to 8.6. It needs a growing season of at least 365 frost-free days, which is why climate matters as much as soil.
USDA Zones
10-13
USDA PHZM 2023
Soil pH
6.8 - 8.6
USDA PLANTS Database
Sun
Full Sun
plant_species_v5.csv
Drainage
Data pending
plant_species_v5.csv
Frost Tolerance
22°F
plant_species_v5.csv
Frost-Free Days
365+
plant_species_v5.csv
Start the season right
Plant ironwood in full sun with at least 6 hours of direct sun, once the soil has warmed and frost risk has passed.
Match the soil
Ironwood prefers pH 6.8 to 8.6 (USDA PLANTS Database). A quick soil test from your local Extension lab tells you whether to add lime or sulfur to land in band. It fixes its own nitrogen, so skip the high-nitrogen feed and instead dust the seed with a matching rhizobium inoculant at sowing.
Water steadily
Keep the root zone evenly moist through establishment. Match watering to the plant's drainage preference and your local rainfall.
Keep it in good form
Prune ironwood 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 — ironwood isn't known to be toxic to dogs or cats. (Source: ASPCA.)
Where Ironwood thrives
Ironwood is hardy across USDA zones 10 through 13. 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 10–13·Where Ironwood growsOpen map →
Continental US shown — Alaska and US Pacific territories sit outside the federal map's polygon dataset.
On USDA hardiness-zone overlap, Ironwood can grow in these states:
See if Ironwood will thrive on your land
Zone averages are a start. Your exact soil pH, drainage, sun exposure, and frost dates shape whether ironwood 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 Ironwood in my zone?
Ironwood grows in USDA hardiness zones 10 through 13 (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 Ironwood?
Most growers plant ironwood after the last spring frost, once the soil has warmed, leaving enough of the season for its 365-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 Ironwood need?
Ironwood 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 Ironwood need?
Ironwood prefers soil pH 6.8 to 8.6 (USDA PLANTS Database). Your report scores your parcel's actual soil against that using USDA SSURGO data.
Is Ironwood safe for pets?
Ironwood is not known to be toxic to dogs or cats based on available data (ASPCA). Always supervise pets around new plantings.