Days to germination: 6 to 10 days
Days to harvest: 60 to 80 days
Light requirements: Full sun or slight shade
Water requirements: Frequent but light watering
Soil: Fertile and rich soil
Container: Quite suitable
Radicchio can be a confusing vegetable for anyone not familiar with it. It’s a leafy salad green, and not related the radish even though the names are similar. Radicchio is also sometimes called Italian chicory to further complicate things, though it is closely related.
The leaves are usually deep red with bright white ribs, and it grows a lot like a head of cabbage. Some varieties produce a tight head, and some are leafier. It has strong tasting leaves that can be noticeably bitter when eaten raw, though that is still the most common way to use radicchio. The flavor is much milder if you cook it.
It’s a perennial, so you once you establish your plants, you can harvest your radicchio for many more years.
The strong taste usually means people eat it sparingly in their salads, but it is a very nutritious plant and probably should be eaten more often. The leaves are high in potassium, folic acid and even vitamin C.
Starting from Seed
Radicchio is a cool-weather plant, so you’ll get the best results with either a spring or fall planting. Since they can handle some light frosts, you can plant your spring seeds up to 4 weeks before your expected last frost date.
For a second fall crop, you can start another batch of seeds about 8 to 10 weeks before you expect to get the first frosts of winter. If your growing season is short, you might find that a fall planting of radicchio won’t thrive because it is still too hot when the seedlings are first growing. If that is the case, stick to the first planting in the spring. You just need to watch your plants so they don’t go to seed in the summer heat.
Work your soil well, and add a very generous helping of compost or aged manure to the soil before any seeds go in. Seeds need to be sown close to the surface, no deeper than 1/4 inch under the soil. Even just a sprinkling of loose soil over the seeds is enough.
Keep your plants watered often, but only a light watering is necessary. Don’t flood the plants. During the hotter months, it’s a good idea to lightly water your radicchio every day to keep the soil moist. This can help prevent your plants from bolting too early. Once they go to seed (bolt), the leaves will almost immediately get too bitter to eat.
You can also protect your plants from the heat with some mid-summer shading. They do need full sun when they are first growing, but when the hot weather arrives, they will do better in the shade.
Another thing that can make your plants bolt early is too much nitrogen, so take it easy with commercial fertilizer. Use a low-nitrogen blend if necessary. If your soil is rich to start with, you probably won’t need to add any fertilizer anyway.
If you are short on garden space, you can grow radicchio in large pots without any problems. Keep it to one plant for every 8 inches of container, and water them frequently. They may even grow better than out in the garden because you can move the pots into shadier surroundings as the season heats up.
Mix your potting soil with compost, and give your radicchio a feeding with low-nitrogen fertilizer after about 4 weeks to keep the nutrient levels up.
Pests and Diseases
Leafy radicchio is vulnerable to some of the same types of pests you will find on many other greens, like various caterpillars and slugs. They chew up the leaves, destroying your harvest if not killing the plants outright. Various methods will work to keep the slugs out of your garden, including commercial pesticides, saucers of beer and liberal dosings of powdered diatomaceous earth. If you check on your radicchio plants regularly, even just picking the caterpillars off will help.
Juice-sucking aphids can also cause problems for your plants, particularly around the large veins or ribs in the leaves. A few aphids won’t do much damage, but large clusters of them will weaken the plant. Frequent sprays with water can help keep them off, and natural pyrethrin-based insect sprays can also be a deterrent.
But overall, there aren’t many insects that like radicchio because of the strong flavor. It’s also very disease-resistant. You can sometimes find powdery white smudges of mildew on the leaves due to high humidity around the plants. Water the soil rather than the leaves, and thin out any extra plants to help with air circulation.
Harvest and Storage
If you are growing a fall crop of radicchio, leave your plants until after the first couple of light frosts if possible. The chill will help take the bitterness out of the leaves, leaving you with much sweeter tasting greens. You can harvest individual leaves, or wait until the plant has matured and take the entire head.
You can tell when it’s ready to harvest by the firmness of the entire head. Once it’s developed into a head, you can cut it off at ground level to harvest. For spring-sown radicchio, you have to also watch that you harvest before the heat causes the plants to go to seed.
Even after you’ve sliced off the entire head, the plant will still come back the next year as long as the roots are not disturbed over the winter.
Like most greens, radicchio doesn’t store very well and is definitely best used fresh. Individual leaves should be stored in the refrigerator, in a plastic bag with damp paper towel to keep it moist. It will stay crisp and fresh for 4 to 5 days this way. If you’ve harvested the entire head, you can keep that in the fridge for up to 2 weeks.