There’s no arguing that the deep burgundy color of radicchio is stunning in the salad bowl, but radicchio is one of those vegetables you either love or you don’t. I find it a bit too bitter for my taste, but my husband is a big fan. To keep peace in the vegetable patch (and the house!), I grow a few radicchio plants every year for him to enjoy in salads of mixed greens.
I’ve grown radicchio in both the spring and the fall, and here in my USDA zone 6 garden, I definitely get better results from a fall-planted crop. Our spring weather is unpredictable, and a few days of warm weather in May spell disaster for radicchio—the flavor becomes even more bitter and the plants quickly bolt. But when I plant radicchio in late summer for fall harvests, the flavor is far more mild.
Radicchio is very frost-tolerant, so late-season plantings last well into November and December around here with nothing more than a layer of floating row cover to protect the plants. If I grow the radicchio in the cold frame and the weather cooperates, I can sometimes manage to harvest as late as January.
The small heads of radicchio only get to be about the size of a small grapefruit so they don’t take up a lot of room in the garden, and after a few light frosts, the flavor tends to sweeten enough for me to enjoy this vegetable right along with my husband, without the challenges of bitterness.
To grow a fall crop of radicchio in colder zones like mine, sow seeds 1/2 inch deep and 1 inch apart anytime between early July and mid-August. Keep the seedbed well-watered until the plants are established, and thin the resulting seedlings to a spacing of 6 inches to give each plant plenty of room to grow.
Before sowing seeds of this and any other fall greens, I always amend my garden soil with 2 to 3 inches of finished compost to replenish the nutrients depleted by earlier crops. The increased organic matter also aids in soil water retention.
I sometimes get impatient and harvest a few baby radicchio leaves before the plants form a head. My husband enjoys these tender, young leaves in mixed salads, but most of the plants are allowed to reach maturity before harvesting.
To harvest full-grown radicchio heads, I slice the plant off at ground level with a sharp knife, leaving the root stump in the ground. I then pile 3 or 4 inches of straw around the root stump to protect it throughout the winter. Come spring, I remove the mulch and the stump will often sprout a new head, resulting in a second harvest of radicchio the following year. I also do the same trick with some varieties of lettuce and I get the same results. When left in the ground, these overwintered stumps often yield the first crops of the season the following April. It gives me a head-start on spring and allows a second harvest from a single planting.