Fertilising guide
How to fertilise 'Castelfranco' Radicchio (Cichorium intybus var. foliosum 'Castelfranco')— schedule & NPK
Also called Castelfranco radicchio, Variegated chicory.
More about 'castelfranco' radicchio
About 'Castelfranco' Radicchio
Cichorium intybus var. foliosum 'Castelfranco' · also called Castelfranco radicchio, Variegated chicory · edible
'Castelfranco' is an Italian heirloom radicchio forming a loose, rose-like head of cream and pale-green leaves speckled with wine-red flecks. A cool-season chicory, it develops its prized colour and mild, gently bitter sweetness as autumn temperatures drop, sometimes after blanching. It matures in about 80-90 days in fertile, moisture-retentive soil and full sun to part shade.
Growth habit: Rosette-forming leafy chicory that opens into a loose, open, rose-shaped head rather than a tight ball. Outer leaves can be tied up or covered to blanch the heart, deepening the cream colour and softening the bitterness as it matures into cool weather.
What fertiliser 'castelfranco' radicchio actually wants — and why
'Castelfranco' Radicchio feeds in two distinct phases — balanced to build the plant, then high-potassium the moment flowering starts to set and fill a heavy crop.
Balanced (even N-P-K) at planting for roots and frame, then switch to a high-potassium ("high-potash") tomato-style feed once the first flowers open — potassium is what sizes and ripens fruit, not nitrogen.
For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for 'castelfranco' radicchio: match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.
How often to feed 'castelfranco' radicchio, and which months
Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For 'castelfranco' radicchio:
Light-to-moderate feeder. A compost-enriched bed plus an occasional balanced liquid feed during leaf growth is enough. Excess nitrogen produces soft, floppy heads more prone to rot and less inclined to colour up. So: a balanced feed or compost at planting, then a high-potash liquid every 1-2 weeks from first flower through harvest across the main season (spring through early autumn).
The dormant-season rule matters more than the exact interval: skip feeding entirely when 'castelfranco' radicchio is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.
What strength to mix for 'castelfranco' radicchio
Follow the crop-feed label rate for 'castelfranco' radicchio — these are calibrated for hungry vegetables. Consistency through fruiting matters more than strength; erratic feeding causes problems like blossom-end rot.
Feeding always goes onto already-damp soil, never dry roots — water 'castelfranco' radicchio first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the 'castelfranco' radicchio watering schedule.
Signs you are over-feeding 'castelfranco' radicchio
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for 'castelfranco' radicchio:
- Vigorous dark-green leafy growth but few flowers or fruit (excess nitrogen).
- Lush foliage hiding the crop; soft growth prone to pests and disease.
- Salt crust on the soil and scorched leaf edges in containers.
Signs you are under-feeding 'castelfranco' radicchio
- Pale, yellowing lower leaves and stunted growth.
- Small fruit, poor set, and a quickly exhausted plant.
- Blossom-end rot and weak cropping from erratic or insufficient feeding.
If the symptoms point at watering, light or roots rather than nutrition, the full 'castelfranco' radicchio care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
In containers, fertiliser salts build up fast — water 'castelfranco' radicchio thoroughly so excess drains from the base each time, and flush pots with plain water every few weeks to prevent a damaging salt build-up.
Organic vs synthetic feeds for 'castelfranco' radicchio
Organic options
Garden compost or well-rotted manure dug in before planting, plus a liquid comfrey or seaweed feed once fruiting starts. UK: comfrey feed or organic Tomorite; US: Espoma Tomato-tone or Neptune's Harvest. Builds soil and feeds in one.
Synthetic / liquid feeds
A balanced feed at planting then a high-potash tomato feed in fruiting — UK: Growmore at planting then Tomorite (Levington) or Phostrogen; US: a balanced 10-10-10 then Miracle-Gro Tomato or a bloom booster.
Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.
Fertilising 'castelfranco' radicchio — frequently asked questions
What fertiliser does 'castelfranco' radicchio need?
Balanced (even N-P-K) at planting for roots and frame, then switch to a high-potassium ("high-potash") tomato-style feed once the first flowers open — potassium is what sizes and ripens fruit, not nitrogen. 'Castelfranco' Radicchio feeds in two distinct phases — balanced to build the plant, then high-potassium the moment flowering starts to set and fill a heavy crop.
How often should I feed 'castelfranco' radicchio?
Light-to-moderate feeder. A compost-enriched bed plus an occasional balanced liquid feed during leaf growth is enough. Excess nitrogen produces soft, floppy heads more prone to rot and less inclined to colour up. Light-to-moderate feeder. A compost-enriched bed plus an occasional balanced liquid feed during leaf growth is enough. Excess nitrogen produces soft, floppy heads more prone to rot and less inclined to colour up. So: a balanced feed or compost at planting, then a high-potash liquid every 1-2 weeks from first flower through harvest across the main season (spring through early autumn).
What strength of feed for 'castelfranco' radicchio?
Follow the crop-feed label rate for 'castelfranco' radicchio — these are calibrated for hungry vegetables. Consistency through fruiting matters more than strength; erratic feeding causes problems like blossom-end rot.
What does over-feeding 'castelfranco' radicchio look like?
Vigorous dark-green leafy growth but few flowers or fruit (excess nitrogen). Lush foliage hiding the crop; soft growth prone to pests and disease. Salt crust on the soil and scorched leaf edges in containers. Staying on a high-nitrogen feed once 'castelfranco' radicchio starts flowering is the classic error — you get a huge leafy plant and a disappointing crop. Switch to high-potash the moment flowers appear.
Should I flush the soil of 'castelfranco' radicchio?
In containers, fertiliser salts build up fast — water 'castelfranco' radicchio thoroughly so excess drains from the base each time, and flush pots with plain water every few weeks to prevent a damaging salt build-up.
Keep reading
- 'Castelfranco' Radicchio care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water 'castelfranco' radicchio — the watering schedule
- The houseplant fertiliser schedule — feeding through the year
- NPK ratio explained — what the three numbers on the bottle mean
- How to fertilise tomato
- How to fertilise pepper
- How to fertilise cucumber
- All 1284 fertilising guides in the Growli library