Achillea

246 DIANTHUS BARBATUS
can be vernalized during the rooting process, but results are contradictory. The
use of supplemental light to enhance the rooting of cuttings reduces the amount
of chilling needed. If temperatures above 100F (38C) occur immediately after
the cold treatment, the benefit of the cold treatment disappears (devernalization)
(Cockshull 1985, Takeda 1996).
Photoperiod: Photoperiod has little effect on flowering if plants are vernalized.
If plants have not been vernalized sufficiently, then LD accelerates flowering
slightly and may produce a higher percentage of flowering plants (Cockshull
1985). If plants have received no cold, flower buds will initiate in SD during the
winter (Takeda 1996).
Field Performance
Yields of 4–10 stems/plant are not uncommon. Transplants should be placed in
the field early enough for plants to establish themselves before cold weather
arrives. If direct sown, seedlings should be thinned to 6–8" (15–20 cm) in the
row (Post 1955). If planted in the spring or summer, flowering will not occur
until the following spring.
Greenhouse Performance
Because sweet william is a cool-loving plant, the greenhouse may be maintained
at 45–50F (7–10C); it is therefore relatively inexpensive to force sweet william
into flower. Plants (seedlings or cuttings) should be grown for 8–12 weeks at
55–60F (13–15C) before applying the necessary cold treatment. When plants
have sufficient roots and 6–12 leaf pairs, temperatures should be reduced to 40–
45F (4–7C) and maintained. Plants flower as temperatures increase in the spring.
Stage of Harvest
Harvest when 10–20% of the flowers in the inflorescence are open.
Postharvest
Fresh: The use of STS and 1-MCP enhances vase life. The vase life of flowers
treated with 1-MCP was up to 4 times greater than control plants (Serek et al.
1995). Flowers persist 7–10 days.
Storage: Flowers may be stored dry at 34–36F (1–2C) or wet at 40F (4C) for 7–
10 days. Few differences have been seen between wet and dry storage (Bang et al.
1996); however, treatment with an ethylene inhibitor is recommended.
Cultivars
Single and double forms are available, nearly all from seed. Time from sowing to
harvest is approximately 40 weeks. Hybrid cultivars, with Dianthus barbatus as