Vegetable · Asteraceae
Radicchio
Cichorium intybus
Let the cool of fall do the work, and radicchio swaps harsh green for deep red and a pleasant bitter edge.
Full sun
Every 3–7 days
60–85 days
USDA 3–9
Overview
So what is radicchio, exactly? It's that red, bitter chicory you find in an Italian salad bowl. It's part of the Asteraceae family, a form of Cichorium intybus, and it's a biennial that most folks grow as a quick fall crop. The head looks a lot like a little red cabbage, but one bite tells you it's chicory through and through: sharp, bittersweet, and even better once a few cold nights hit.
Here's the thing that really sets it apart from lettuce, and it's all about timing. Radicchio wants to finish up in cool fall weather, because the cold is what deepens that red and takes the edge off the bitterness. Try to push it through summer heat and it'll just bolt, turn coarse, and go bitter in a way nobody wants. But get the timing right? The same plant gives you firm, richly colored heads.
It does take a little patience, since you're looking at 60 to 85 days from seed to a finished head. The good news is that steady water and halfway-decent soil handle most of it, and the cool weather takes care of the rest. And because radicchio shrugs off the light frost that would flatten more tender greens, it'll keep your garden going well into the cold months.
Care
The short version: full sun, steady water at 1 to 2 inches a week, and rich soil that drains well, all timed so the heads finish up in cool fall weather.
Light
Radicchio loves full sun, though it'll put up with a bit of partial shade if your late summers still run hot. All that sunlight keeps the plants sturdy, and sturdy plants are the ones that head up firm and nicely colored.
Water
Try to keep that soil evenly moist, somewhere around 1 to 2 inches of water a week. If it dries out or the watering gets uneven, the leaves get more bitter and the heads come out weak, so water a little more often if you're on sandy, fast-draining ground.
Soil
Go with fertile, well-drained soil that's got plenty of organic matter in it. A pH between 6.0 and 6.8 is the sweet spot, just a touch acidic, and honestly most decent garden soil is already pretty close.
Temperature
This is a cool-weather plant, happy anywhere from 19°F to 75°F (-7°C to 24°C). Young plants can even take a frost down to about 20°F (-7°C), and that fall chill isn't a problem at all, it's exactly what deepens the color and softens the bitterness.
Humidity
There's no humidity number to fuss over here, since ordinary outdoor air does the job. What matters way more is airflow, because leaves that stay crowded and damp are the ones that run into trouble.
Feeding
Mix a complete fertilizer like 10-10-10 into the bed before planting, then side-dress with a little nitrogen about 4 weeks after transplanting. Once the heads start forming, ease off the nitrogen, or you'll end up with leafy growth instead of a nice tight head.
Pruning
You don't really prune radicchio at all. Just pull off the outer leaves when they get damaged or diseased, and clear away old debris so pests and disease don't get comfortable.
Size & spacing
These plants stay pretty small, about 6 to 12 inches (15 to 30 cm) tall and a similar 8 to 12 inch (20 to 30 cm) across. Give each one that much space so the heads can fill out and a little air can move through.
When to plant
Radicchio's really a fall crop at its core. Start the seeds in summer, get the plants outside in late summer, and then just let the heads tighten up as things cool down, because that cold snap is what brings out the color and flavor.
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 radicchio troubles come down to one thing, and that's heat showing up at the wrong time. Bolting and loose heads? That's a crop stuck in summer warmth. Pests and disease tend to show on the leaves. Find what matches below and jump on it early.
Yellowing, twisted, stunted growth that looks deformed
This one's aster yellows, a phytoplasma that leafhoppers carry around, and there's no fixing a plant once it's got it. Best thing to do is pull the sick plants and destroy them so they can't pass it along. Keeping leafhoppers and weedy hosts under control is really your only defense here.
Fix:
- Remove and destroy infected plants
- Control leafhoppers
You get a tall flower stalk instead of a head
What's happening here is bolting, and nine times out of ten it's summer heat setting it off. Once the plant runs to seed it goes coarse and bitter, so go ahead and harvest it before it gets any worse. The real answer is timing: sow so the heads come in during cool fall weather instead of the middle of summer.
Fix:
- Harvest promptly before quality declines further
- Replant timing so heads mature in cool fall weather
Heads just won't tighten up
A loose head usually means it stayed too warm while the plant was trying to close up, or the soil went dry and hungry. Keep the water even and the feeding steady, and that helps a lot. After that, it's about timing the crop so the heads form in the cool of fall, which is when radicchio's at its best.
Fix:
- Ensure consistent moisture and adequate fertility
- Adjust planting date so heading coincides with cool weather
Chewed-up leaves, little holes, and toppled seedlings
A few different pests like radicchio: cutworms snip seedlings off at the base, slugs leave slime and chewed holes, and flea beetles leave the foliage speckled with tiny shotholes. Handpick or trap whatever you can, and insecticidal soap handles aphids and caterpillars. Just scout regularly and keep the bed weed-free, and most of them never get going.
Fix:
- Handpick or trap slugs and cutworms
- Use insecticidal soap or appropriate controls for aphids and caterpillars
Toxicity
Good news here: there's really nothing to worry about with radicchio. It's a salad vegetable, the leaves are grown to be eaten, and it's got no toxic risk for people, pets, or livestock. So if a pet grabs a leaf on the sly, it'll be totally fine.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Cats are totally fine around radicchio. A curious nibble won't hurt them, even if leafy greens like this aren't really cat food.
Dogs None
Dogs have nothing to worry about with these leaves. If one sneaks a bit of your salad, it won't do any harm.
Horses Safe
Horses are safe with radicchio, no question. Chicory greens are a familiar forage for them and carry no toxic risk.
Rabbits Safe
Rabbits can eat radicchio just fine, and plenty of them actually like the bitter leaves. Just mix it in with other greens instead of feeding it solo.
Livestock Safe
Cattle, goats, and sheep graze on chicory with no trouble at all, and it's even planted on purpose as pasture forage.
Birds Safe
Backyard hens and other birds can peck away at the leaves however they like. There's nothing in radicchio that'll hurt them.
People Safe
For people, radicchio's a salad vegetable meant to be eaten, raw or grilled. That bitterness? It's the whole point, not a warning sign.
No special handling precautions; an ordinary edible salad green.
Varieties
You'll only run into a handful of radicchio types in most gardens, and they mostly split two ways: the round Verona style and the long, tapered Treviso style. Here are the ones worth knowing.
Rossa di Treviso
This Italian heirloom puts out long, tapering heads marbled with red and white.
Rossa di Verona
This is the one that makes the round, classic radicchio head, deep red with bright white ribs running through it.
Giulio
Giulio's a reliable round-headed type that does really well in a home garden.
Firebird
Firebird's a solid cultivar that people count on for heading up consistently.
How to propagate
Radicchio grows from seed, and it's pretty flexible: you can sow it right in the bed, or start it under cover and transplant it out for a fall crop.
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 grows from seed, and you've basically got two options. Sow it straight in the ground and it puts down one strong taproot, or start it in a greenhouse over summer and transplant it for a fall crop. Give the seeds 65°F to 70°F (18°C to 21°C) and they'll sprout their best, since germination really tapers off above 80°F (27°C), and figure on 60 to 85 days from sowing to a finished head.
Myths
Radicchio's just a red kind of lettuce.
It sure looks that way, but no. Radicchio's a chicory in the Asteraceae family, not a lettuce, and that's exactly why it tastes so bitter. It needs a longer stretch too, about 60 to 85 days, and its color and flavor really only kick in once cool fall weather shows up.