Cut Flowers - Crop Post-Harvest: Science and Technology - page 446

19
Cut Flowers

Daryl Joyce and John Faragher

Cut flowers and foliage represent an important international
industry, with an estimated world trade of approximately
$US4.6 billion per year (Staby & Robertson 1982; Behe
1993; Wills et al . 1998; Laws 2002). Their farmgate value
is high and they are utilised in value-adding operations,
such as bunching in bouquets. Aesthetically, cut flowers
contribute to the general quality of life through their
natural beauty. They are the subject of fashion and the
articles of design (Figure 19.1). Cut flower types and
colours are associated with social trends (e.g. sunflowers
have regained popularity in recent times). Cut flowers are
used to convey special messages (e.g. on Mothers' Day
and St Valentine's Day).
Flowers are often transported long distances, under
adverse conditions, from the place of production to markets
(e.g. from southern hemisphere and tropical countries to
Europe, United States and Japan). This makes good post-
harvest handling imperative, but often difficult. Post-
harvest losses during marketing of cut flowers within the
United States have been estimated to be 20% (Hardenburg
et al . 1986).
The ornamentals industry covers a broad range of
product types, including fresh and preserved (e.g. dried)
cut flowers and foliage and potted seedling, foliage and
flowering plants (Gross et al . 2004; Wills et al . 1998; Reid
2002). This overview focuses on fresh flowers, but also
considers preserved flowers (Joyce 1998).

BIOLOGY
The optimal application of post-harvest technology
benefits from an understanding of product biology (Wills
et al . 1998). Commercial cut flowers are often complex,
compound structures, including stems, leaves, flowers and
sometimes bracts and fruit. Each of these parts may develop
and age differently after harvest. Cut flower longevity is
often expressed as 'vase life', the time in which flowers
are in the vase before they display some characteristics
that make them unacceptable (e.g. petal wilting or drop;
Figure 19.2). This is usually measured under standard
conditions of 20°C and 60-70% relative humidity (RH)
(Reid & Kofranek 1980; Joyce 1996).
Genotype is a fundamentally important factor determin-
ing cut flower longevity (Ashman & Schoen 1994). Different
genera vary widely in their vase lives (e.g. from a few days
for Dutch iris to several weeks for spray carnations). Vase
life can also vary markedly among genotypes within species
and genera. Vase life of cut grevillea flowers ranged three-
fold, from three days for Grevillea wickhamii Meisn. to
nine days for G. whiteana McGill (Joyce et al . 1996).
Ferrante et al . (2002) reported a range in foliage longevity
for cut alstroemeria flower stems from five to 18 days.
Post-harvest longevity can also vary with phenotype,
which is the interaction of genotype with environment and
management factors. These factors include cumulative
light energy, production temperatures, water and nutrients