Romanesco

Romanesco: plant 50 cm (20 in) apart in the row and 75 cm (30 in) between rows, 1 per square. Good neighbours: Dill, Onion, Celery.

Key facts

Spacing in the row	50 cm (20 in)
Between rows	75 cm (30 in)
In a 30 cm (1 ft) square	1 per square
Sun	Full sun, 6–8 hours a day
Root depth	40 cm (16 in)
Height when grown	50 cm (20 in)
Crop rotation group	Cabbage family
Support	None needed

Sowing and germination

How it is started	Started in trays, sown straight into the bed
Seeds per hole	2
Plants kept after thinning	1
Seeds per metre of row	4
Sowing depth	1.2 cm (0.5 in)
Soil temperature	from 4 °C, best 18–29 °C
Days to emerge	5–10 days
Light while germinating	Light makes no difference
Before sowing	nothing needed
When to sow	Indoors 6 weeks before the last frost; outdoors before the last frost; soil at least 10 °C

From seedling to plant

After emergence	14–20 °C; take the cover off as soon as they show
Pricking out	at 2 true leaves
Takes transplanting	Easily
Hardening off	7–10 days
Life cycle	Annual
Cold tolerance	Takes a light frost → hardy, takes hard frost
Soil	Rich, with compost, stays moist, pH 6.5–7.5
In a pot	15 L, 30 cm (11.8 in)
Watering	Water when the soil is dry two fingers down; while heads form
Feeding	Hungry; at planting, while growing
Support and training	None needed

Harvest and planning

Days to first harvest	85–110 days, from planting out
Ready when	The head is tight and bright chartreuse green
Harvest window	All at once, 2–3 weeks
Typical yield	0.6–1.2 kg per plant
Botanical family	Brassicaceae
Watch out for	Cabbage white caterpillars, flea beetles, clubroot, aphids

Good neighbours

Why, with the sources →

Plan Romanesco in your garden

Open the free planner, drop Romanesco onto a bed and see how many plants fit.

Start Planning Your Garden

Sowing and harvest

Sow indoors	Mar–Apr
Sow outdoors	May–Jun
Harvest	Sep–Nov

My dates for this crop

My country Last spring frost where I live

Give the date once and this page, the sowing calendar and the planner all follow it.

Months for a temperate climate: about a month later in the north and a month earlier in the south. Give your own last frost date for exact dates.

What to plant next to Romanesco →

From the same family

Plants of the Brassicaceae family share diseases and pests, so they follow each other in the rotation only after a break.

Sources

The values on this page marked as checked come from these sources: spacing, sowing depth, germination, soil, timing and safety notes, each against the source named here.

Cole Crops (Current Information Series) — University of Idaho Extension for: when to sow, between rows, spacing in the row; checked 2026-10-30
Soil temperature conditions for vegetable seed germination (J.F. Harrington; reviewed 2024) — Oregon State University Extension for: days to emerge, soil temperature; checked 2026-10-30
Broccoli, Brussels sprouts, cabbage and cauliflower: planting — UC Statewide IPM Program for: sowing depth; checked 2026-10-30
Soil Temperature Conditions for Vegetable Seed Germination (GN 154, after J.F. Harrington, UC Davis) — UC Cooperative Extension, UC ANR for: soil temperature; checked 2026-10-30

More in Cabbage family

← All plants