PlantSowGrow
How to grow Romanesco
Brassica oleracea Botrytis Group
Lime-green, spiralled heads with a nutty flavour — a fascinating cross between broccoli and cauliflower.
At a glance: Sow mid March to late April, harvest from mid August.
When to sow, plant and harvest
Timed for a typical UK garden (last frost mid-April). The app uses your own town's frost dates.
Growing Romanesco: what it needs
- Light
- Full sun · 6+ hours a day
- Watering
- Water steadily — stress makes small heads
- Soil
- Fertile, well-drained soil
- Spacing
- 60 cm
- In pots
- Best in the ground
- Feeding
- A general feed before sowing or planting
- Harvest
- About 130 days from sowing
- Hardiness
- USDA zones 3–9
- Difficulty
- Intermediate
Step by step
- Mid March – late April · 4 weeks before the last spring frost
Sow Seeds Indoors
Sow in modules or small pots of seed compost under cover.
- 5–10 days after “Sow Seeds Indoors” · Late March
Check Germination
Seedlings should appear in 5–10 days. If sown outdoors, thin to 60 cm apart when big enough to handle.
- 14–21 days after “Check Germination” · Early April – mid April
Pot On Seedlings
Move seedlings into 9 cm pots (or keep in modules) when they have their first true leaves.
- Early May · 3 weeks after the last spring frost
Harden Off
Stand plants outside by day for 7–10 days before planting out.
- Mid May – mid June · 4 weeks after the last spring frost
Plant Out
Plant out 60 cm apart and water in well.
- 0–3 days after “Plant Out” · Mid May
Net Against Pests
Cover with fine insect mesh or netting straight after planting to keep off pigeons, cabbage white caterpillars and flea beetles.
- 90–111 days after “Plant Out” · Mid August – early September
Start Harvesting
Cut when the head is full-sized and still tight.
- 30–60 days after “Start Harvesting” · Mid September – mid October
Finish and Clear
Clear the remains to the compost heap once cropping ends.
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