Achillea

28 POSTHARVEST CARE
extends vase life anyway, so keep the water fresh. Add household bleach to the
water, and rinse the bottom half of the flower stems before cutting under water.
Bacteria can also block the ends of stems. Clean containers and acidified
water greatly reduce this problem, as do commercial floral preservatives, which
contain antibacterial and antifungal agents, such as 8-hydroxyquinoline citrate
or sulfate (8-HQC, 8-HQS). Additional agents should not be necessary.
Conditioning: Conditioning or hardening of cut stems restores the turgor of
wilted flowers. In general, demineralized water should be used when conditioning
solutions are prepared. When stems are placed in solutions, they should be
held at room temperature initially (a few hours to overnight) then placed in cold
storage for several hours. Warm water (110F, 43C) is highly recommended for
restoring turgor only in badly wilted stems. Badly wilted stems, especially those
with woody stems, may benefit from being placed in hot water (180–200F, 82–
93C) prior to being placed in room temperature solutions.
Postharvest Solutions
Rehydration solutions: This is an essential step after harvest. Freshly harvested
flower stems are placed in water to restore turgidity, a process called rehydration.
Rehydration solutions contain no sugar and are essentially used to jumpstart
the flow of water through the plant’s plumbing system. They include a germicide
and wetting agent and have a pH around 3.5. If possible, rehydration
should take place immediately after cutting.
Pulsing solutions: Generally, pulsing solutions are used to provide sugars
(sucrose or glucose, 2–20% added to flower food) and silver compounds (STS),
and occasionally to reduce leaf yellowing (cytokinins) and as a germicide (5- to
10-second silver nitrate dip on specific crops). The uptake of all solutions is
affected by both the temperature of the solution and the temperature of the air.
Colder temperatures require a longer pulsing period than warmer temperatures.
Bud-opening solutions: Flowers that are cut bud-tight respond to bud-opening
solutions prior to sale to the final consumer. These consist mainly of a fresh
flower food and additional sugar. Nell and Reid (2000) suggest that bud-opening
solutions be used at 70–75F (21–24C), 60–80% relative humidity, and relatively
high light.
Fresh flower food: These solutions are known and sold as flower preservatives,
but the term “fresh flower food” is kinder and gentler, and that is a good thing.
Most consist of sugar (the food), a biocide to reduce bacterial growth, and an
acid to reduce the pH; sometimes they contain a growth regulator to reduce leaf
yellowing or an anti-ethylene substance. Fresh flower food can increase vase life
up to 75% (Nell and Reid 2000), and while not all flowers will respond dramatically,
few will be harmed by the products.
In-house mixing: Flower preservatives, silver solutions, bactericides, bud openers,
conditioners, and sugar solutions are all part of the postharvest jargon.
While these various components can be mixed in the back room, what is the
point? It is doubtful that homemade solutions will significantly differ from commercial
mixes, and often mistakes are made in the process, resulting in solu-