Flower Care - Ethylene Gas
Esthetically, flowers and fruit combine beautifully in floral arranging, however this combination often comes at a price, shortened flower life. While floral designs and gift baskets combining flowers and fruit look great. the pairing can be a death knell for some flowers. Why? An invisible culprit known as ethylene. Knowing a little bit about ethylene will assist you in making choices about the flowers and fruit you can combine without any detrimental effects.
What is Ethylene?
Ethylene is an odourless, colourless gaseous plant hormone that exists in nature and is also created by man-made sources. Not easily detectable, in nature the largest producers are plant and plant products (IE. fruits, vegetables and floral products) which produce ethylene within their tissues and release it into the surrounding atmosphere. It is also a byproduct of man-made processes, such as combustion and is used in some industrial manufacturing.
Ethylene, is often referred to as the 'death' or 'ripening hormone' and plays a regulatory role in many processes of plant growth, development and eventually death. Fruits, vegetables and flowers contain receptors which serve as bonding sites to absorb free atmospheric ethylene molecules.
What does Ethylene do?
It's overall effect on plant material is to hasten ripening, agingand eventually spoilage.
The common practice of placing a tomato in a paper bag to hasten ripening is the classic example of the action of ethylene on produce. Increased levels of ethylene contained within the bag released by the tomato itself, serve as a stimulant and in turn initiate the production of more ethylene, which in turn is reabsorbed by the tomato....and so the cycle continues
Ethylene has in fact proved useful in the produce industry and is used to speed the ripening of some produce such as bananas which are commonly picked green then exposed to ethylene gas in transit to speed ripening to ensure nice yellow bananas at the time of sale.
Ethylene and its effect on flowers
So that brings us to flowers and the affects of ethylene on them. Some of the effects of ethylene on flowers include:
- Bud and leaf abscission ( falling off)
- Leaf yellowing, transparency
- Loss of deep colour
- Flower or petal drop
- Irregular bud opening ("sleepy carnations" are the classic example)
- Premature death
While ethylene may have it uses and prove beneficial to certain segments of the produce industry, none of the above effects are desired in fresh cut flowers. It is estimated that upwards of 30% of flowers perish prematurely due to the harmful effects of ethylene.
Unfortunately it does not take very much ethylene to cause problems in flowers;
- Levels of 100 ppb (parts per billion) can cause damage over time periods greater than 24 hours
- Levels of 250 ppb (parts per billion) can cause damage in as little as 12 hours
Lets put the above numbers in perspective, 100 drops of food colouring in 26,400 gallons of water equates to 100 ppb! So it is safe to say a little ethylene goes a long way when it comes to damaging flowers.
What flowers are effected?
Sensitivity to ethylene varies among flower, fruit, and plant species. It even varies among a particular species varieties, as an example lets take roses a flower that all of us are familiar with. In fact lets look at two varieties of red roses, a "Charlotte" rose is quite sensitive to ethylene, while on the other hand a "Forever Young" rose is not as sensitive. Generally, flowers that are recognized as being highly sensitive to ethylene are treated at the farm level with anti-ethylene products to ensure longer life. Good examples of this are gypsophilia (babies breath) and carnations, both are very sensitive so are treated to protect against exposure. In the case of carnations treatment generally increases vase life by a factor of 3-4 times. All flowers are effected to some degree, but particular flowers fall into a group considered "Ethylene Sensitive".
Ethylene Sensitive Flowers
*** Not all varieties of these flowers fall into the Ethylene Sensitive category
What can be done to minimize the effects of ethylene on flowers?
While there are solutions for minimizing the effects of ethylene gas in commercial flower applications (farms, wholesalers, and retail flower shops) they are not practical for the occasional flower buyer or for use in homes. These solutions generally involve the use of a material that absorbs ethylene, one such material is a mineral named Guerite.
More than 2,300 hours of testing at the University of SouthFlorida determined the mineral Guerite - absorbs up to 5% of its weight in ethylene gas and up to 11% of its weight in water. This mineral is used in some food storage products to elongate the lifespan of foods.
As well, temperature plays an important role, as ethylene sensitivity is less of a problem at temperatures below 4º C (40º F). This is one of the reasons that maintaining the "cold chain" is so critical at all levels of flower production and distribution, starting at the farm all the way through to the retailer you purchase your flowers from.
The best advice for flowers in the home is to simply avoid placing them in close proximity to ethylene sources.
Ethylene is produced from a variety of sources including;
- Produce (Apples, apricots, avocados, ripening bananas, blueberries, cantaloupe, citrus fruit (not grapefruit), cranberries, figs, guavas, grapes, green onions, honeydew, ripe kiwi fruit, mangoes, melons, mushrooms, nectarines, okra, papayas, passion fruit, peaches, pears, peppers, persimmons, pineapple, plantains, plums, prunes, quinces, tomatoes and watermelon)
- Propane heaters
- Auto exhaust, gas powered fork lifts
- Cigarette smoke
- Other Flowers (more pronounced with aging)
- Bacterial and Botrytus (fungal disease)
Some simple rules to follow are;
- Never place flowers near fruit or vegetables.
- Avoid placing flowers in areas where they will be exposed to heavy cigarette smoke or exhaust from
propane heaters or automobiles, trucks, etc.
- As flowers age remove dying or older flowers from close proximity to fresher flowers.
Keep flowers out of higher temperatures. While it is not practical to keep your flowers at less than 40º F in your home placing them in a very warm area will shorten their life overall.