KENNEWICK -- Are you old enough to remember the "green revolution" of the 1970s when live houseplants were popular?

Veritable jungles grew in homes across the county.

While many grandmothers had perfected the indoor growing of African violets, the public wanted more choices.

Universities researched the types of plants that could be grown under the low level of light found in buildings. They also developed soilless potting mixes that provided better growth than plain unsterile garden soil.

Garden writers wrote book after book on the care of houseplants. An entire indoor plant industry was "sprouted" and there were live plants growing in shopping malls, office buildings and homes.

So why have homes and businesses shifted from their tropical plant decor of the '70s and '80s to a paucity of live plants today?

I don't know, but I can guess some of the reasons. Houseplants take effort and time, both precious commodities with today's very fast paced lifestyles.

Houseplants can be messy with dead leaves, repotting, and water leaking from pots. If not nurtured and provided with enough light, houseplants can turn into downright ugly or even dead specimens.

In the late 1980s, when the indoor plant craze had started to wane, NASA research revealed the ability of certain indoor plants to help purify air by removing harmful organic pollutants. Because of the energy crisis and the skyrocketing costs of heating and cooling, more and more homes were being built to be energy efficient. The more energy efficient the homes, the greater the buildup of these harmful organic pollutants of trichloroethylene, benzene and formaldehyde.

These pollutants were given off by the various adhesives, building materials, foam insulation, paint and other finishes used to construct, furnish and clean our homes. While the standards for many of our building materials and paints have changed to reduce our exposure, they're still present in our homes.

When NASA research revealed that certain indoor plants could help "clear the air," it was presumed that it was the green leaves that did all the work. Later research revealed that it was the plant, the roots and the soil working together. For plants to be most effective as air purifiers, it's desirable to "maximize air exposure to the plant root-soil area."

(Researchers noted that even better results could be obtained if fans with charcoal filters were used to pull air into the soil. )

The general recommendation based on the NASA research is to place at least 15 adequately sized houseplants (plants in six- to-eight inch or larger pots) in a 1,800 square foot house. The plants found to be most effective at cleansing polluted indoor air are (Aglaonema modestum) Chinese evergreen, (Chamaedorea sefritzii) bamboo or reed palm, (Chlorophytum comosum) spider plant, (Dracaena deremensis) Janet Craig or Warneck dracaena, (Dracaena fragrans 'Massangeana') cornstalk dracaena, (Dracaena marginata) red-edged dracaena (Epipiremnum aureum) golden pothos, (Ficus benjamina) weeping fig, (Hedera helix) English ivy, (Philodendron domesticum) elephant ear philodendron, (Philodendron scandens 'oxycardium') heartleaf philodendron, (Philodendron selloum) selloum philodendron, (Sansevieria trifasciata) snake plant and (Spathiphyllum) peace lily. While not year-round houseplants, potted mums and gerbera daisies were also very effective as air purifiers.

So go green, start a jungle in your house and clear the air.

* Marianne C. Ophardt is a horticulturist for the Washington State University Benton County Extension Office.