You've probably heard that putting an aspirin or two in the water keeps cut flowers fresh. If you tried that with the flowers you were fortunate enough to get on Valentine's Day, you'll soon discover there's no teeth in that often-used home remedy. Aspirin just doesn't work. In fact, the medicine cabinet isn't a good place to turn for plant-care products.

Take the shine off

Neither is the refrigerator. For years, people have used milk or mayonnaise as "natural" ways to shine the leaves of houseplants. It turns out that using a soft cloth dipped in one or the other does make the leaves look shiny. That glossy surface, however, only holds onto dust and grime, which makes your plants look dirty even sooner than they would have if you hadn't shined them at all.

So skip the plant shiners, homemade or commercially manufactured. Instead, wipe leaf surfaces clean with a cloth dipped in plain old water. (Lukewarm is best.) If the foliage seems particularly greasy or sticky, dissolve a few drops of mild dishwashing liquid in the water first, then wipe the leaves gently. But don't try to scrub leaves squeaky clean.

Up in the air

If you really want to improve the health of your houseplants, you could try talking to them while you tend them. Getting right in their faces, so to speak, and yelling at them might be even better.

It's odd but true that conversing with plants gives them a slight boost. That's because humans inhale oxygen and exhale carbon dioxide, while plants give off oxygen and soak up carbon dioxide. (Because commercial growers can't chat with all of their plants, some pump additional CO2 into their greenhouses to improve plant production.)

While we're on the subject of plants and people, let me put a lingering misconception to rest. At one time, plants were removed from hospital rooms at night because it was thought that they sucked too much oxygen from the sick room. Plants do use a small amount of oxygen at night, but it's far too little to affect the air quality in the room. Unless you have allergies, there's no reason you can't keep flowers or houseplants in your bedroom.

Use the packet

OK, back to aspirin. If it isn't the key to keeping flowers fresher longer, what is? Well, how long a flower lasts depends a lot on the flower itself.

Flowers with staying power include alstroemeria, carnations, daisies, mums, orchids and other exotics such as anthurium, bird-of-paradise and protea.

But there are things you can do to make any kind of cut flowers last:

• Use the packet of floral preservative that comes with the flowers.

• Make sure the vase is clean.

• Fill the vase with fresh, lukewarm water.

• Change the water every couple of days.

• After a few days, cut a half-inch off the base of each stem so the flowers can continue to take up water.

If you do all of the above, you'll be able to enjoy your bouquet for days, maybe even weeks. And that's something worth singing about.

Deb Brown is a garden writer and former extension horticulturist with the University of Minnesota. To ask her a gardening question, call 612-673-7793 and leave a message. She will answer questions in this column only.