All plants

Radicchio

Cichorium intybus

Asteraceae · sunflower family

Matures
80–90 days
Harvest
Once · Annual
Sun
6–8+ hrs
Spacing
8–12 in
Botanical engraving of Radicchio

Planting window

When to sow, by microclimate — foggier blocks run a different calendar than sunnier ones.

JanFebMarAprMayJun
Foggy◐●●◐◐
Sunny◐◐◐
JulAugSepOctNovDec
Foggy●●●◐◐
Sunny●●●◐◐
Well-suitedMarginalNot suited

Sunlight

How well it does at each level of direct sun per day.

<2 hrsNot suited
2–4 hrsNot suited
4–6 hrsMarginal
6–8 hrsWell-suited
8+ hrsWell-suited
Well-suitedMarginalNot suited

Soil depth

Root room it needs — useful for sizing raised beds and containers.

6–10"Not suited
10–15"Marginal
15–18"Well-suited
18–24"Well-suited
Well-suitedMarginalNot suited

Spacing

Room each plant needs — along the row and between rows — for sizing beds.

In-row
8–12 in
Between rows
18 in

Growth habit

The shape it makes in the bed and how tall it gets — what tells you whether to give it a trellis, a stake, or just room.

Habit
Low mound
Mature height
6–12 in

Low and self-supporting — no staking needed.

How to start it

Sow it where it grows, or raise it under cover and set it out — and how far ahead to start the seedlings if it's the latter.

Usually
Direct-sow
Direct-sowWell-suited
TransplantMarginal

Sown straight into the bed it will grow in.

Well-suitedMarginalNot suited

Getting started

How it goes in the ground — how deep to sow or set it, and the soil temperature it needs to wake up. The cold-soil floor is the real limiter for direct-sowing in a foggy SF spring.

Started from
From seed
Ideal soil temp
70–75°F
Sow depth
0.25 in
Time to emerge
7–10 days

Germinates between 45–85°F; happiest around 70–75°F.

30°F110°F
IdealWorkable

Pests & diseases

What tends to trouble this crop — what it is, what you'll see, and what to do about it, least-toxic first.

Pests2

Aphids
What it is
Aphids have soft pear-shaped bodies with long legs and antennae and may be green, yellow, brown, red, or black depending on the species and the plants they feed on. A few species appear waxy or woolly due to the secretion of a waxy white or gray substance over their body surface.
What you'll see
Low to moderate numbers of leaf-feeding aphids aren't usually damaging in gardens or on trees. However, large populations can turn leaves yellow and stunt shoots; aphids can also produce large quantities of a sticky exudate known as honeydew, which often turns black with the growth of a sooty mold fungus.
What to do
Before planting vegetables, check surrounding areas for sources of aphids and remove these sources. On the other hand, these aphid-infested weeds can sometimes provide an early source of aphid natural enemies.
Source
Worms and Loopers
What you'll see
Light to dark green insects that chew holes and hide in leaves. Adult loopers are gray or brown moths while cabbage worms are white butterflies.
What to do
Control worms and loopers with appropriate insecticides or biological measures.
Source

Diseases2

Fungal Root Rots
What you'll see
Wilting and reduced plant vigor which occurs during forcing.
What to do
Cultural practices that facilitate air movement will reduce disease severity.
Source
Viruses
What you'll see
Stunting of growth. Interveinal yellowing and brittleness in older and lower leaves.
What to do
Control aphids which transmit the disease.
Source

Sources

Every figure above is backed by these.

  • UC Small Farms Networkbacks plantingWindow, daysToMaturity, startMethod · UC Small Farms radicchio page: 'Sow seeds 1/4 to 1/2 inch deep from September through March' and 'the summer heat can cause bolting and tip burning, so August and September plantings are recommended' (backs the Aug-Mar window, summer = no). Days: '80 to 85 days in the Salinas Valley'. Start method: UC Small Farms radicchio: 'Sow seeds 1/4 to 1/2 inch deep from September through March' — sown in place.
  • UC Master Gardeners, Sonoma County (Planting Summary)backs plantingWindow, daysToMaturity, inRowSpacing, lifecycle, harvestStyle, rowSpacing, startMethod · Vegetable Planting Summary, 'Chicory and Radicchio' row: 80-90 days, 12 in in-row spacing. Notes 'Plant in spring only in cooler areas' — the basis for the foggy/sunny split (foggy cooler blocks keep Feb-May spring plantings; sunnier blocks drop spring to no and favor the fall window). Habit and harvest: annual, once — consistent with this source's planting-summary row. Between-row spacing 18 in (Chicory and Radicchio row). Start method: Vegetable Planting Summary, Chicory and Radicchio row: method D (usually direct-sown).
  • Utah State University Extensionbacks sunlight, inRowSpacing, plantingDepth, startMethod · USU 'Chicory in the Garden' (Cichorium intybus): 'Chicory is a cool-season vegetable that prefers a sunny location' (full sun; 4-6 hrs = maybe). 'Seeded or transplanted radicchio should be spaced 8 inches between plants in the row' — the 8-in floor combined with Sonoma's 12 in gives 8-12. Agronomy only; USU timing is Utah-calibrated and not used. Planting depth 1/4 in: 'Plant chicory seeds 1/4 inch deep.' Start method: USU Extension chicory: 'Seeded or transplanted radicchio should be spaced 8 inches between plants in the row' — transplanting is done, but no source here publishes a seed-to-transplant time for it.
  • UC Master Gardeners, Santa Clara County (Containers)backs soilDepth · No radicchio row; assigned moderate-depth (12-18 in) rather than shallow because chicory is taprooted — it heads shallowly but sends a deep taproot, so it wants more depth than leaf lettuce (assigned by parity with the moderate-depth root/heading crops).
  • Cornell University Home Gardeningbacks germination, growthHabit · Cornell Home Gardening radicchio (Cichorium intybus): germination 45–85°F, optimum 70–75°F; emergence 7–10 days. Growth habit: Growing Guide lists 'Height: 0.5 to 1 feet', 'Spread: 0.5 to 1 feet', and 'Shape: cushion, mound or clump' — habit low-mound (freestanding leafy head/rosette, no support); height 6–12 in (0.5–1 ft). This is the harvested head form, not the tall bolted flower stalk.
  • USDA GRIN Taxonomybacks botany