It's a gas!

Alexander Lyubavin/Flickr

Alexander Lyubavin/Flickr

Just when you thought you understood all the common hazards in your own little home, along comes an invisible menace to pit your salad greens, wilt your cut flowers and threaten the well-being of your windowsill plants.

You’ve probably been an unwitting co-conspirator, transporting this colorless, odorless promoter of premature rot and death in bags of seemingly innocuous groceries, lugged home from the supermarket.

That apple, that avocado, that innocent-looking pear — they’re all sitting around on your countertops and in your fridge, emitting high levels of ethylene gas. And you can’t make them stop.

Ethylene is a naturally occurring plant hormone given off by many plants as they approach maturity. It’s known as the “ripening hormone,” which sounds okay, and the “death hormone,” which doesn’t.

You may even have taken advantage of it by putting a tomato, avocado or banana in a paper bag to hasten ripening. Contained by the bag, increased levels of ethylene released by the fruit are reabsorbed, stimulating the production of yet more ethylene. The result? Faster ripening, soon followed by faster aging and decay. Throw an apple in the bag and you're really upping your game.

The same gas can build up in your refrigerator, where, with stealth and cunning, it can toughen your asparagus, cause spotting in leafy greens like lettuce and make watermelon go all mushy.

Do you also store flower bulbs, like tulips and daffodils, in the refrigerator prior to planting to keep them in dormancy? The evil ethylene can cause the embryonic flowers inside the bulb to abort or can bring about abnormal growth, including excessive leafiness and deformed blossoms. Who knew?

I stumbled across this information researching a recent piece on forcing bulbs. While harmless to humans, clearly ethylene is a force to be reckoned with vis-à-vis the plants around the house.

Rushing home, I dragged the extra tulips and daffodils out of the fridge — the ones I never got to plant — and sped them to safety in the basement. Then I stood there, shifting from foot to foot, with a bag of Macintosh apples in one hand and a not-quite-ready-to-eat mango in the other. What to do?

"Conversation with an Apple and a Banana"   Andromeda/Flickr

"Conversation with an Apple and a Banana"   Andromeda/Flickr

On one windowsill, where I usually ripen fruit, was a paperwhite just sprouting and a slip of a Dendrobium my orchid pal Dennis gave me. Orchids, I’ve read, are ethylene-sensitive. On the other windowsill, I had a pot of tulips and a Christmas cactus of unknown susceptibility. Yikes! Danger everywhere!

Ethylene was used with no real comprehension by the Romans to ripen figs in sealed storerooms, but in modern times its role was uncovered by accident. Lemon growers kept newly picked green fruit in sheds warmed by kerosene heaters until they turned yellow and were ready for market. When alternate heating methods were used, ripening lagged. Research pinpointed the small amounts of ethylene given off by burning kerosene as the critical factor.

Today, the cut flower and produce industries are concerned, since unchecked ethylene exposure can cause up to 40 percent of their inventories to die or rot prematurely.

With produce, you know what happens — ugly, blackened bananas fit only for daiquiris and punky apples fit only for applesauce. In the case of cut flowers, ethylene can cause blooms to close prematurely, referred to as “going to sleep;" make flowers open rapidly, called a “blown head;" or keep buds from opening at all, called "disappointment." Leaf yellowing and leaf drop also may result. Carnations, that staple of cut bouquets, are especially sensitive.

Commercial growers and florists use ethylene absorbers in the form of beads or pellets that change color as they absorb and neutralize the gas. This isn’t too different from those bags of pellets you hang to keep basements and closets from smelling musty.

But what’s a homeowner to do? Generally, we consume produce pretty quickly, so it doesn’t become a big deal. But it’s worth knowing about ethylene effects so you can isolate evil-doers.

The highest gas producers include apples, apricots, avocados, cantaloupes, kiwis, nectarines, papayas, peaches, pears, plums and passion fruit. Bananas, figs, honeydew melons, mangoes and tomatoes are moderate producers. Low ethylene emitters include cherries, citrus fruits, leafy vegetables, potatoes, blueberries, cucumbers and pineapples.

Keep the worst offenders away from ethylene-sensitive produce like asparagus, eggplant, green beans, leafy salad greens, summer squash and watermelon — and cut flowers, orchids and flower bulbs. Then hope for the best.

As for my initial dilemma, the mango wound up in the living room on a table in front of the sunny French doors ’til rosy and edible. The apples, peeled and sliced, went into a pie. Faced with this new threat, I fell back on an old principle: If you can’t beat ’em, eat ’em.