Vegetable · Asteraceae
Radicchio
Cichorium intybus
Grown into cool fall weather, radicchio trades harsh green for a deep, ember-red that lifts the autumn table.
Full sun
Every 3–7 days
60–85 days
USDA 3–9
Overview
Radicchio is the red, bitter chicory that gives an Italian salad its edge and its color. A form of Cichorium intybus in the Asteraceae family, it grows as a biennial that the garden treats as a brief fall project. The head sits on the plate like a small ruby cabbage, but its taste is unmistakably chicory: bracing, bittersweet, and at its most elegant after the season's first cold nights.
What gives radicchio its place in the cool-season garden is timing. It comes into its own in cool fall weather, when the chill turns the color deep and the flavor refined. Force it through summer heat and the appeal is lost: the plant bolts and the taste turns coarse. Time it to the season, though, and it becomes the crop that carries a plot from tired late summer into a vivid autumn.
It rewards a little patience, asking 60 to 85 days from seed to a table-ready head. Steady water and good soil set the stage, and the cooling weather does the finishing. Because radicchio takes the light frosts that flatten softer greens in stride, it keeps the garden dressed in color well after the summer beds have gone quiet.
Care
The short version: full sun, even water of 1 to 2 inches a week, and rich, free-draining soil, all arranged so the heads come to color in the cool of fall.
Light
Give radicchio a spot in full sun, with a little partial shade tolerated where late summer stays warm. Good light is what builds the sturdy plants and firm, well-colored heads that make the crop worth a place in the plot.
Water
Keep the soil evenly moist, about 1 to 2 inches of water a week. Let it run dry or water it unevenly and the flavor turns harshly bitter and the heads go slack, so reach for the hose more often on quick-draining sandy ground.
Soil
Set radicchio into fertile, well-drained soil worked through with organic matter. A pH of 6.0 to 6.8, just shy of neutral, gives it the footing it likes best.
Temperature
Radicchio is a cool-season plant at heart, at ease across 19°F to 75°F (-7°C to 24°C). Young plants stand up to frost near 20°F (-7°C), and rather than a threat, the autumn cold is the very thing that enriches the color and rounds off the bitterness.
Humidity
Ordinary garden air suits radicchio, so there is no humidity figure to manage. The detail that matters is airflow, since leaves left crowded and damp are the ones that invite problems.
Feeding
Turn a complete fertilizer such as 10-10-10 into the bed before planting, then follow with a nitrogen side-dressing about 4 weeks after transplanting. Ease off the nitrogen once heads begin to form, or the plant spends itself on leaves instead of the tight center you want on the plate.
Pruning
Radicchio asks for no pruning. Simply lift away the outer leaves as they tire or turn diseased, and keep debris cleared so pests and disease find no quarter.
Size & spacing
The plants keep a tidy, compact frame, standing 6 to 12 inches (15 to 30 cm) tall and spreading 8 to 12 inch (20 to 30 cm) wide. Give each that room so the heads fill and air moves easily between the plants.
When to plant
Radicchio belongs to the fall calendar. Sow in summer, settle the plants out in late summer, and let the heads gather color as the air cools, since that seasonal chill is what gives the crop its depth and character.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Early to mid summer (start seeds indoors in July for transplanting in August for a late-season fall crop)
- Plant: Transplant in late summer (August) for fall harvest, or direct sow about 75-85 days before the anticipated maturity/harvest date
- Harvest: Fall (heads harvested as cool weather improves color and flavor)
Hardiness
USDA hardiness zones: 3–9
Temperature: down to -40°C
Troubleshooting
Most of what goes wrong with radicchio traces to warmth arriving at the wrong moment. Bolting and loose heads follow a crop caught in summer heat, while the leaves tell you about pests and disease. Match the look below and step in before it spreads.
Yellow, twisted, and stunted growth with deformed shoots
The trouble is aster yellows, a phytoplasma carried between plants by leafhoppers, and once it arrives there is no cure. Lift the affected plants and destroy them so it travels no further. Keeping leafhoppers and weedy hosts in check is the only lasting safeguard.
Fix:
- Remove and destroy infected plants
- Control leafhoppers
A flower stalk rises where the head should sit
This is bolting, and summer heat is nearly always the cause. A plant that runs to seed grows coarse and bitter and loses its place at the table, so harvest it before things worsen. The real remedy is the calendar: sow so the heads mature in cool fall air rather than midsummer heat.
Fix:
- Harvest promptly before quality declines further
- Replant timing so heads mature in cool fall weather
Heads stay open and never close
A loose head usually points to warmth lingering through heading, or to soil gone dry and lean. Keep the moisture even and the feeding up to settle the plant. Then set the crop so it heads in the cool of fall, the season that shows radicchio at its finest.
Fix:
- Ensure consistent moisture and adequate fertility
- Adjust planting date so heading coincides with cool weather
Chewed leaves, pinholes, and seedlings felled at the soil
A handful of pests find radicchio: cutworms fell young seedlings at the base, slugs trail slime and leave ragged holes, and flea beetles freckle the leaves with tiny shotholes. Handpick or trap the reachable ones, and turn to insecticidal soap for aphids and caterpillars. Regular scouting and a clean, weed-free bed keep most trouble at bay.
Fix:
- Handpick or trap slugs and cutworms
- Use insecticidal soap or appropriate controls for aphids and caterpillars
Toxicity
Radicchio brings no worry to the kitchen or the garden. Grown purely as a salad vegetable, its leaves are made for eating and hold no toxic risk to people, pets, or livestock. A pet that samples a leaf comes away unharmed.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Radicchio sits easily in a home with cats. A curious nibble does no harm, though these bitter greens hold little interest for most cats.
Dogs None
Dogs share a garden with radicchio without concern. A pilfered leaf of this salad green passes with no ill effect.
Horses Safe
Horses take no harm from radicchio. Chicory is a long-familiar forage and carries no toxic risk for them.
Rabbits Safe
Rabbits eat radicchio safely, and many take to its bitter edge. Offer it as one note in a mix of greens rather than the whole meal.
Livestock Safe
Cattle, goats, and sheep graze chicory with ease, and it is even sown on purpose as pasture forage.
Birds Safe
Backyard hens and other birds are free to peck the leaves. Radicchio holds nothing that would harm them.
People Safe
For people, radicchio is a salad vegetable made for the table, whether raw or set over the grill. Its bitterness is a pleasure to cook around, not a warning.
No special handling precautions; an ordinary edible salad green.
Varieties
A short, well-chosen list of radicchio types shows up in most gardens, sorted between the round Verona heads and the long Treviso heads. These are the ones worth planting for the table.
Rossa di Treviso
An Italian heirloom whose slender, tapering heads carry streaks of deep red over white.
Rossa di Verona
The variety that shapes the round, classic radicchio head, deep red laced with bright white ribs.
Giulio
A dependable round-headed choice that settles happily into a home garden.
Firebird
A reliable cultivar admired for the steadiness of its heading.
How to propagate
Radicchio begins from seed, either sown where it will grow or raised under cover and moved out to fill the fall garden.
SeedModerate
Start indoors in summer (e.g., July) for transplanting in late summer, or direct sow; seeds germinate best at 65-70°F and germination drops above 80°F. · Roughly 60 to 85 days from sowing to a mature head depending on cultivar and conditions.
Radicchio is grown from seed by one of two routes to suit the plot. Sow it directly and it anchors a single strong taproot, or raise it under glass through summer and transplant it into a fall crop. Start the seed at 65°F to 70°F (18°C to 21°C) for the best germination, since it drops away above 80°F (27°C), and allow 60 to 85 days from sowing to a finished head.
Myths
Radicchio is just a red lettuce by another name.
The likeness is only skin deep. Radicchio is a chicory of the Asteraceae family, not a lettuce, and that lineage is the source of its bitterness. It also keeps a longer calendar of about 60 to 85 days, and its color and flavor only come into their own once cool fall weather settles in.