Romanesco is a perennial grown for the harvest, ready about 85 days after sowing. It's hardy across USDA zones 2 through 11. Its flowers are a moderate draw for honeybees and native bees, even though the harvest is the prize. As a brassica (the cabbage family), give it a fresh bed each year — away from where its relatives just grew — so the soil-borne pests and diseases of the family never get a foothold.
Romanesco — the short answer
Romanesco: grown in zones 2–11, part sun, pH 5.5–8.5, about 85 days to maturity.
- USDA zones
- 2–11
- Manual horticultural correction (source not retained); NC State Extension and Missouri Botanical Garden, with the remaining rows from other published sources or Growable Ground compilation
- Soil pH
- 5.5–8.5
- FAO ECOCROP
- Sun
- Part Sun
- Growable Ground Plant Database
- Days to Maturity
- 85 days
- Growable Ground Plant Database
- Frost-kill temperature
- 23°F
- Growable Ground Plant Database
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 Romanesco on your exact land.
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What Romanesco is
Romanesco grows as a perennial and reaches around two feet at maturity.
How to grow Romanesco
Romanesco grows in USDA zones 2 through 11 and is ready to harvest about 85 days after planting. Romanesco does best in part sun — at least 4 hours of direct sun a day — and soil from pH 5.5 to 8.5, on well-drained ground. It needs around 1,200 growing degree days to mature and a growing season of at least 60 frost-free days, which is why climate matters as much as soil.
USDA Zones
2-11
USDA PHZM 2023
Soil pH
5.5 - 8.5
FAO ECOCROP
Sun
Part Sun
Growable Ground plant catalog
Drainage
well (dry spells)
Growable Ground plant catalog
Frost Kill Temperature
23°F
Where cold starts killing growing tissue. Not a winter-survival floor — a dormant perennial takes far colder, which its hardiness zone answers.
Growable Ground Plant Database
Minimum Growing Temperature
41°F
Below this it stops growing rather than dies — a pace limit, not a survival limit.
Growable Ground Plant Database
Days to Maturity
85 days
Growable Ground plant catalog
GDD Required
1200+
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
2 ft
Growable Ground plant catalog
Frost-Free Days
60+
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 romanesco in part sun with at least 4 hours of direct sun. It grows in the cool halves of the year, so sow it in spring or late summer rather than waiting for midsummer heat.
Match the soil
Romanesco prefers pH 5.5 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
Romanesco is ready about 85 days after sowing. Watch for cultivar-specific ripeness cues and pick at peak.
Where Romanesco thrives
On hardiness alone, romanesco grows across most of the country — its range (USDA zones 2 through 11) is unusually wide. 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 2–11 spans average winter lows from -50°F to 50°F (USDA PHZM 2023). Across the 50 states and DC, that band covers 48 outright and splits 3 more down the middle — and which side of that line your land sits on changes the answer.
Zones 2–11·Where Romanesco growsOpen map →
Continental US shown — Alaska and US Pacific territories sit outside the federal map's polygon dataset.
Where Romanesco stands, state by state
Romanesco is rated for zones 2–11 — a cold floor USDA puts at -50 to -40°F. Across the 50 states and DC, 48 sit fully inside that band, the line runs through 3 more, and 0 sit outside it — and inside every split state, the same line runs on at county grain.
Fully inside zones 2–11
48 states
3 of 48 shown
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 Romanesco
Growing guides for romanesco
In rotation planning, romanesco counts as a Brassica — beds recover best when brassica crops don’t follow each other in the same spot year over year. (Growable Ground derivation — crop-rotation group from botanical family)
Related plants in vegetable
Good to know
Good news for pet owners — romanesco isn't known to be toxic to dogs or cats. (Source: ASPCA.)
Romanesco offers moderate value to bees and other pollinators. (Source: Pollinator Partnership.)
Before you harvest romanesco, 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 romanesco 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.
Your land is one point inside Romanesco'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 Romanesco will thrive on your land
Zone averages are a start. Your exact soil pH, drainage, sun exposure, and frost dates shape whether romanesco 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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How we know this about Romanesco
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•USDA PHZM•ASPCA
Frequently asked questions
Can I grow Romanesco in my zone?
Romanesco grows in USDA hardiness zones 2 through 11 (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 Romanesco take to grow?
Romanesco is ready to harvest about 85 days after planting. Your local frost dates and soil temperature move that window earlier or later.
When should you plant Romanesco?
Romanesco is a cool-season crop, so it goes in during the cool halves of the year — early spring, and again in late summer for a fall planting — rather than at the height of summer heat. Your local frost dates set the exact window — a Growable Ground report reads them for your address.
How much sun does Romanesco need?
Romanesco does well in partial sun — around 4 hours of direct sun, and it takes some afternoon shade in stride. That flexibility makes it a good match for a bed the house or a nearby tree shades for part of the day. A Growable Ground report maps how the sun actually falls on your land, hour by hour, so you can set it where the light lines up.
What soil does Romanesco need?
Romanesco prefers soil pH 5.5 to 8.5, on well-drained ground (FAO ECOCROP). Your report scores your parcel's actual soil against that using USDA SSURGO data.
Does Romanesco attract pollinators?
Yes — romanesco's flowers are a solid nectar source for honeybees and native bees. (Source: Pollinator Partnership.)
Is Romanesco safe for pets?
Romanesco is not known to be toxic to dogs or cats based on available data. Always supervise pets around new plantings. (Source: ASPCA.)