Down the row, plants grow every 10 to 15 inches depending on the stand before thinning. Raw seed can be precision seeded with a vacuum-type seeder, but other precision seeders require coated seed. Some radicchio has been transplanted using transplanting modules or plugs. In the warmer inland valleys, the summer heat can cause bolting and tip burning, so August and September plantings are recommended. Growers should experiment to determine the best planting date for each variety.
Some varieties perform best on lighter, better-drained soils.
Harvest rates are low, sometimes in the 20 to 40 percent range. Many of the plants will produce either unmarketable heads or no heads at all. Nonforcing radicchio forms a head under normal growing conditions, whereas a forcing variety will form a head only after freezing weather. Upon peeling back the dead outer leaves, you will find the red head inside. Radicchio may be a host for lettuce mosaic.