Ethylene gas is an odourless, colourless, natural plant hormone. It is also a by-product of man-made processes like combustion. Ethylene gas speeds up the process of deterioration in sensitive flowers and can even kill them.
In a natural environment ethylene is emitted by ripe fruit as well as dead or damaged flowers and foliage. In the man-made environment, ethylene is emitted by cigarette smoke, motor vehicle exhausts and closed storage environments such as refrigerators and shipping containers.
Some flower varieties are more sensitive to ethylene gas than others. Flowers affected by ethylene will visually show signs of leaf and flower drop, wilting, petal drop or petal curl and are signs you will see. This can be seen in stock, gypsophila, sweet William, carnations and liliums.
Alstromeria, freesia and roses may fail to open if exposed to ethylene. It is important not to confuse natural petal drop with that caused by ethylene, some flowers like delphinium and larkspur will drop their petals easily, and therefore ethylene exposure may not be the cause.
To counteract effects in sensitive flowers some growers treat flowers with silver thiosulphate solution or STS. Flowers treated with STS will become resilient to ethylene.
E.g. STS treated delphiniums can last up to 3 weeks with no petal drop at all.
Flowers treated with STS are more costly to purchase. Ask florists if flowers have been STS treated. If you are selling always point this out to clients. The spray is not harmful to the consumer, but the process has strict controls by growers.
STS is beneficial to many flowers as it inhabits the action of ethylene. Most of the flowers sensitive to ethylene have been shown to respond well to treatments that inhabit, or delay ethylene production by flowers.
STS treatment is done by a grower as the immediate post-harvest treatment is the most beneficial.
Some commercial floral preservatives such as Chrysal A.V.B. (R) and Florissant 100 (R) may be convienient for florists to uses.
When using STS you must wear gloves as the concentrate leaves brown stains that take ages to wear off your skin and never washes out of clothing.
STS must be disposed of according to the strict guidelines.
• Store at low temperatures. I.e. close to 1 degree except for tropical flowers.
• Ensure adequate ventilation. – A little air movement will dissipate ethylene.
• Flowers treated with STS are not harmful to the consumer.