Archive for Sunday, January 7, 2001

One bad apple

Ethylene gas can cause premature decaying of fruits and cut short the life of cut flowers

January 7, 2001


"An apple in the pot makes the plant bloom a lot." Or so the saying goes.

More than an old wives' tale, a few apple slices placed in the container of a houseplant, especially in one from the bromeliad family, may entice the plant to bloom, even if it has been reluctant to do so in the past.

We've also been cautioned about the harm caused by a rotten apple in the barrel.

The reason is the ethylene gas given off by the apple. Ethylene, released by the tissue cells that have undergone damage to them during slicing or decay, acts as a stimulant to the plant to bloom.

Ethylene gas, commonly known as "ripening gas," is a naturally occurring plant hormone. It is an odorless, colorless, tasteless gas that is released during the natural ripening process. Apples, like many other fruits and vegetables, release the senescence-promoting substance.

Many people take advantage of nature's method to ripen produce that has been picked too early. Homemakers, for example, have always used ethylene gas to hasten the ripening of green tomatoes or unripe bananas, perhaps without even knowing it.

Unripe fruit is placed in a paper sack, either by itself or with a few apple slices, and left at room temperature. Exposure to the ethylene gas naturally released by the green fruit or the sliced apples, which is being trapped within the bag, causes the fruit to ripen within a few days.

In fact, commercial growers use ethylene gas to "ripen" produce that has been picked green for shipment to grocery stores.

As helpful as that sounds, the news about ethylene gas is not all good.

Some fruits and vegetables may be subject to premature decay when exposed to ethylene. Plus, fruit that is damaged or diseased gives off more ethylene gas and hastens the process of decay to surrounding fruit.

So, be sure to toss the overripe fruit into the compost pile if it is not intended to be eaten soon. In other words, find that rotten apple and get it out of the barrel.

Bulb precautions

Under certain conditions, ethylene gas can be detrimental to some plants. It may shorten the flower life of cut flowers, inhibit the development of immature flower buds and damage developing flowering buds.

Keep this in mind when displaying bouquets of fresh flowers, set out purposely to brighten winter days.

Fortunately, not all flowers have the same degree of sensitivity to ethylene gas. Carnations are highly susceptible to its negative effects. Lilies, freesias, agapanthus, anemone, dahlia, gladiolus and Dutch iris are moderately susceptible.

Generally, daffodils and tulips are not susceptible, although the tulip variety "Paul Richter" is extremely sensitive.

In addition, exposure to ethylene gas can cause excessive leafiness in plants.

Another caution: Ethylene gas is especially damaging to some bulbs.

Gardeners often place bulbs, dug up from a previous season, in the refrigerator for prolonged chilling prior to planting. In an enclosed space of the refrigerator, ethylene gas, released by fruits and vegetables also being stored there, may cause the embryonic flowers inside bulbs to abort or not fully form. The result may be stunted growth from the bulb.

Keeping producers of ethylene gas away from or in a separate compartment will lessen the likelihood of damage to chilling bulbs.

Foods to watch

Foods that are high producers of ethylene gas are apples, apricots, avocados, kiwi, cantaloupe, papaya, nectarines, passion fruit, peaches, pears and plums.

Bananas, figs, honeydew melons, mangos and tomatoes produce a moderate amount of ethylene gas. Low producers are cherries, citrus fruit, leafy vegetables, potatoes, cucumbers, pineapples and blueberries.

Factors that may determine the effects of ethylene gas exposure include ventilation, temperature and the stage of development of the flower, plant or bulb.

So, whether you wish to prolong the life of fresh cut flowers in your home during the winter, store bulbs in the coolest place in the house or have fruits and vegetables edible faster or longer, remember ethylene gas is around all the time.

Carol Boncella is education coordinator at Lawrence Memorial Hospital and garden writer for the Journal-World.

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