Radicchio

Radicchio (Cichorium intybus var. foliosum) is the deep red Italian bitter green that turns up in high-end salad mixes and on restaurant menus as a composed salad base. It’s a chicory - the same species as common chicory, Belgian endive, and radicchio di Treviso. The deep red and white color comes from anthocyanin pigments that develop in cool temperatures; those same pigments don’t form in summer heat. Grow radicchio in summer and you’ll get loose, green, intensely bitter leaves that are nearly inedible. Grow it for a fall harvest and you’ll get tight red heads with balanced bitterness. Timing is the whole game.

What you’re actually growing

C. intybus var. foliosum encompasses several regional Italian types, and they’re meaningfully different:

Chioggia type (‘Palla Rossa,’ ‘Rossa di Verona’) forms compact, round heads with deep red leaves and white ribs. This is what most North American seed catalogs sell when they list “radicchio.” It’s the most forgiving type for home gardens.

Treviso type (‘Rossa di Treviso’) forms elongated, torpedo-shaped heads with a more pronounced white rib. It’s sharper in flavor and more cold-sensitive than Chioggia types. More work, better flavor for those who want it.

Castelfranco type produces pale green and red-spotted loose heads that look unlike the compact red heads of Chioggia or Treviso. Milder in bitterness, more delicate in texture.

For a first planting, start with a Chioggia type. They form heads reliably in most climates, tolerate more variation in fall temperatures, and are more available through mainstream seed suppliers.

The ROI case

Radicchio retails at $4.00-$6.00/lb at specialty grocers and farmers markets (USDA AMS Specialty Crop Market News, 2023). A $2.99 packet plants a generous row. Heads average 0.5-1 lb at harvest. A 10-foot row with 10-12 plants yields 5-12 lbs.

Fresh radicchio is rarely found in conventional grocery stores and is often sold at premium prices where it does appear. For cooks who use it regularly, growing it is genuinely economical compared to specialty grocery pricing. For cooks who have never tried it, don’t commit a bed to it before you’ve eaten it at least twice.

Growing requirements

The timing formula for radicchio: count backward from your first hard frost (28°F or colder). Chioggia types need 60-85 days from transplant to harvest. For a harvest window of October through November in zone 6, transplant seedlings in late July or early August.

Starting from seed indoors: sow 6-8 weeks before transplant date. Radicchio germinates readily at 65-75°F in 7-14 days. Thin to one strong seedling per cell before transplanting.

Space transplants 10-12 inches apart in rows 18 inches apart. Radicchio doesn’t need much space, but crowding reduces air circulation and increases disease pressure.

Soil pH 6.0-7.0. Average fertility is fine; radicchio doesn’t need particularly rich soil. Work in 2 inches of compost before transplanting.

Water 1 inch per week. Consistent moisture through head formation produces tighter, heavier heads. Drought stress results in loose, very bitter heads.

In the 2-3 weeks before harvest, the outer green leaves die back and are replaced by the tight red inner head. This is normal. Some growers cut back the outer leaves at this stage to allow the inner head to receive full light and air circulation, which improves head quality.

What goes wrong

Bolting in summer heat is the main failure mode. Radicchio sown or transplanted too early - when it will mature in August heat rather than September-October cool - produces loose, non-heading plants with near-inedible bitterness. Move the entire planting later if this is your problem.

Soft rot (Erwinia carotovora) causes the head to collapse and turn mushy, typically from the base. It’s a bacterial infection favored by wet soil and poor air circulation. Improve drainage, space plants adequately, and avoid overhead watering.

Tipburn (brown leaf margins) from calcium deficiency appears on the outermost head leaves during rapid growth. It’s cosmetic; remove affected outer leaves.

Aphids concentrate inside the head as it tightens. Inspect heads weekly from the outside. Once aphids are inside a tight head, they’re difficult to reach. Prevention is easier than treatment - monitor plants before heads fully form.

Harvest and storage

Cut heads at the base when they feel firm and dense under gentle hand pressure, similar to a small cabbage. The outer green leaves can be stripped away; the red interior is the product. A head that goes too long in the ground after forming eventually loosens and deteriorates.

Store whole heads in the refrigerator unwashed for 1-2 weeks. Cut radicchio turns brown at cut edges quickly. Use cut heads within 1-2 days.

In mild climates (zone 7+), radicchio can be cut in fall, the roots left in place, and secondary growth cut through winter - the ratoon shoots are smaller but flavorful.

---

Related crops: Arugula, Endive

Related reading: Succession Planting Calendar - how to schedule fall brassica and chicory plantings to hit the harvest window correctly