Introduction and Literature Review

Commercial cut flower production encompasses an
incredible array of plant materials including fresh and dried/preserved flowers,
stems, and berries. Each year a wide variety of new cultivars and species are
made available from plant breeders, propagators, and suppliers. The National
Annual and Perennial Cut Flower Trial Programs, established in 1993 and
administered by North Carolina State University and the Association of Specialty
Cut Flower Growers (ASCFG), evaluates 50 to 70 new cultivars annually for
greenhouse and field production (Dole 2001 a,b,c). The cultivars are tested at
approximately 35 locations in the United States and Canada, primarily at
commercial cut flower producers, but also at a few universities and cooperative
extension providers. Much useful production and marketing information is
collected, including yield, stem length, and market appreciation ratings.
However, postharvest life, a key component of a successful cut flower cultivar
is not yet evaluated. Many successful new cut flower species, including Campanula
‘Champion’ and Zinnia ‘Benary’s Giant’ were first given
widespread testing and publicity through the trials. New species have become an
important component of the cut flower industry but many wholesalers and
retailers are obviously reluctant to handle large numbers of new cuts until
specific postharvest information is available. Most of the current information
is for traditional cut flowers (Nell et al., 2000); however, this information is
not readily transferable to the many promising new species being evaluated.
Postharvest information specifically tailored to these new species must be
available as they are first entering the markets.

A number of factors must be examined in
developing the optimum postharvest handling procedures for a new cut flower. Cut
flowers vary greatly in their sensitivity to ethylene with symptoms including
leaf, flower and bud abscission, bud abortion, rapid flower senescence, epinasty
and decreased vase life (Nichols, 1966; Woltering and van Doom, 1988).
Concentrations as low as 100 parts per
billion and exposure times as little as four hours can lead to damage of some
species (Abeles, et a!., 1992; L. H??yer, personal
communication).

The ethylene blocker, silver thiosulfate (STS),
was developed as a pretreatment to prevent ethylene damage and gained widespread
acceptance in the cut flower industry (Beyer, 1976; Halevy and Kofranek, 1977).
Problems with registration, however, led to the lack of STS-containing products
available to growers, wholesalers, and retailers. Recently, however, new
STS-containing products have been registered for use on cut flowers (G. Smith,
personal communication).

Due to previous problems with registration and to
environmental concerns over silver, researchers looked for a variety of other
anti-ethylene agents (Serek et al., 1995; Sisler et al., 1983, 1996). The
anti-ethylene agent 1-methylcyclopropene (1-MCP), initially developed at North
Carolina State University by Drs. Sister and Blankenship and further researched
by Drs. Reid, Nell, Serek and others, has been widely accepted by the
floriculture industry. Further research is needed to determine which species
will benefit from the use of STS and/or 1-MCP and the optimum rates and handling
procedures.

Storing cut stems in coolers benefits the grower,
wholesaler and florist by extending the production season, allowing storage of
excess production, improving production efficiency, and enabling long-term
shipment (Goszczynska and Rudnicki, 1988; Nowak and Rudnicki, 1990). Recommended
storage temperatures for cut flowers depend on the particular species and
cultivar, but generally vary between 0 and 4 ¬?C (32 and 29 ¬?F). Cut stems
could either be stored wet in water or preservative solution or dry in a
polyethylene plastic or wax-lined box.

Vase life can be extended by pretreatments and
pulses, which are short-term treatments (generally 24 h or less) conducted just
after harvest (Nowak and Rudnieki, 1990). A pretreatment may consist of placing
stems in heated water (approximately 38 >C [100 ¬?F]) or in a commercial
hydrating solution to enhance water absorption or
applying an anti-ethylene compound, such as STS or 1-MCP (Serek et al., 1995)
to prevent ethylene damage.

Cut stems may benefit from the addition of
sucrose in the vase solution to increase rate and number of buds opening,
improve petal coloration, and extend vase life (Halevy and Mayak, 1979; Nowak
and Rudnicki, 1990; Sacalis, 1993). Sucrose can be applied in pulse solutions of
0.5% to 25% from a few hours to 2 days or in vase solutions of 0.5% to 7% (Goszczynska
and Rudnicki, 1988). In addition, the vase life of many species is reduced when
stems are marketed in floral foam. Commercial products are typically used by
producers to provide the sucrose, acidifiers and antimicrobial agents required
during postharvest.

We have recently determined optimum postharvest
handling procedures for several specialty cut flowers (Bosma and Dole, 2002;
Redman eta!., 2001). For example, Campanula ‘Champion Blue’ and ‘Champion
Pink¬í stems can be stored at 2 ¬?C (36 ¬?F) either wet or dry with no
difference in vaselife (Bosma and Dole, 2002). Stems pretreated for 4 h with 38
¬?C (100 ¬?F) deionized floral solution [water adjusted to pH 3.5 with
citric acid plus 200 ppm 8-hydroxyquinoline citrate (8-HQC)] followed by a 5%
sucrose pulse solution produced the longest vase life (10.3 days) while
maintaining high quality. Stems had an average vase life of only 3.3 days when
placed in floral vase foam but lasted 10.0 days without foam. Many other new
specialty cut flower species require this postharvest research to reach their
full potential in the marketplace.