Organic Radicchio: Growing and Seed Saving Info
Downloadable version of Radicchio Growing and Seed Saving Info
Radicchio is a cool season annual in the Asteraceae/Compositae family,
which includes lettuce, endive, escarole, chicory, globe artichoke, sunflower,
Jerusalem artichoke, salsify, and burdock. Radicchio has similar culture to
lettuce, but produces very tight heads with blanched interiors and unique
bitter flavor. Radicchio is a popular component of mesclun mix because of its
unusual color and sophisticated flavor. There are several types:
radicchios are narrow and upright with green outer leaves and crispy
radicchios have upright, elongated heads with burgundy interior leaves
that have bright white ribs
radicchios have round and slightly flattened, densely packed heads with
bright magenta interiors
Radicchio does well in the same conditions as lettuce, preferring cool,
well-drained, loose soil. As with lettuce, use 50-75lbs Nitrogen/acre, ~150lbs
Phosphorus and Potassium/acre. Side-dress with N 3-4 weeks after planting. When
transplanting, use 2lbs/50 gallons starter fertilizer, 4-8oz per plant.
Full sun to part shade.
Direct seed 3 seeds every 8”.
Radicchio does best in the cool weather of spring, fall, and early
winter, and fall crops tend to have fewer problems and produce larger heads.
Direct seeding is not recommended in early spring because of the risk of
cold-induced bolting. Sow in a greenhouse in plug trays (2 seeds/plug, thinned
to one) with ¾” tapered cells and a fine-textured starting mix. Cover seeds
lightly with vermiculite. Ideal germination temp is 75°F (day) and 68°F
(night). Feed with liquid fertilizer once seedlings have germinated. Seedlings
should be ready to plant out in 3-4 weeks.
The use of row cover is not recommended for radicchio except when
threatened by heavy frost.
Radicchio can withstand light frosts, just peel off damaged outer
leaves. Leafier varieties are more frost-tolerant. Color and flavor benefit
from extreme fluctuations between day and nighttime temperatures.
Chicories are generally drought-tolerant but require even moisture for
uninterrupted growth. Irrigation is recommended during dry periods.
Radicchio may bolt in hot, dry weather. Provide adequate moisture.
Choose varieties like Leonardo F1 and Virtus F1 for summer plantings.
About 20,000 seeds/oz.
At a rate of 3 seeds every 8”: 220’/1M; 1,100’/5M; 2,200’/10M;
Begin harvesting 6-10 weeks after planting out seedlings. Heads are
firm when mature and will not continue to grow after this point (except to
bolt). Heads hold better in the field in cool fall weather. Ideal size is about
5” in diameter for Chiogggias, 7-8” tall for Trevisos and 10” tall for
Sugarloaf. Leaves pulling away or heads becoming pointy are early signs of
bolting. Use a sharp harvest knife to cut plant at the base of the head, being
careful not to cut the head itself. Heads should be harvested in cool weather
or chilled immediately. Heads are usually trimmed for sale.
Heads will keep for 3-4 weeks if refrigerated in a perforated plastic
bag or tote.
In moist, damp conditions bottom rot may occur, but radicchio is much
less susceptible than lettuce.
Radicchio will easily go to seed if allowed. The flowers are
insect-pollinated and can cross pollinate with other radicchios, endives, or
Wild Chicory, which is very commonly found. For pure seed, isolate by ½ mile or
cage plants. It can be difficult to separate seeds from flowers; crush the
dried flowers to release the seeds. Seeds will be viable for 4-8 years starting
with approximately 70% germination.