Making your house a green house

It's ironic: Houseplants grow best in spring and summer when days are long and sunny, but we pay more attention to them in fall, as days grow shorter and cloudier.

The reason? Tending houseplants lets us exercise green thumbs through the winter, while giving our homes a living, breathing touch of nature.

But houseplants have different requirements for care in summer than they do in winter. Follow these tips to keep your plants growing well and looking good this winter.

Light

Most houseplants need to be by windows where they'll receive direct light part of the day. Lack of adequate light slows a plant's growth. New leaves will be smaller and farther apart. Old leaves may drop because the plant is unable to maintain all its foliage. Both Dieffenbachia and Ficus benjamina are notorious for losing their lower leaves when they don't get enough light.

With the weak winter sun, there's no need to worry about "burning" the foliage. Plants such as African violets, which grow well in a north window in summer, will be perfectly fine in a west or south-facing window.

Water

Because homes are cooler in winter, it takes longer for water to evaporate from potting soil. And, because their growth has slowed, houseplants use water more slowly. So while you need to continue to water your plants thoroughly, wait a bit longer between watering times unless your home is unusually warm and dry.

Be sure to use water that's at room temperature or barely lukewarm. Cold water, straight out of the tap, can damage houseplants, many of which are native to the tropics.

Fertilizer

All plants make their own food by converting light energy to sugars. Fertilizers provide supplementary minerals that are needed when plants are actively growing. Because houseplants grow slowly, if at all, in winter, their need for fertilizer is reduced.

Unless you have a plant that's growing rapidly, hold off fertilizing until mid-February or early March, when longer days trigger new growth. If you do fertilize during the winter, be sure to mix it at half the strength recommended on the label.

Temperature

Lower indoor temperatures slow a houseplant's use of stored food reserves, which helps the plant adapt to fewer hours of daylight. For most indoor plants, daytime temps that range from the low 60s to low 70s and drop 5 to 10 degrees at night work well. And although plants can withstand cool air, cold drafts from entryways or leaky windows can be damaging. So keep plants away from doors that open to the outside and be sure to lower the shades or close the drapes at night to protect plants from cold window panes once the sun goes down.

Grooming

It's particularly important to keep plants clean in winter. Periodically wiping leaves with a soft, damp cloth removes dust as well as any insect or mite eggs. Clean leaf surfaces improve light penetration, and are less attractive to houseplant pests. The bonus? Your plants will look better, too.

Deb Brown is a garden writer and former extension horticulturist with the University of Minnesota.

Chinese evergreen: This compact plant is available in many variegated versions, mostly green and silver, but some have pink or red colors.

Heart-leaf philodendron: This trailing vine has dark green, heart-shaped leaves. A newer variety sports dark green and lime green variegated leaves.

Pothos: A similar vine to heart-leaf philodendron, pothos has variegated green and gold leaves. There is a variety with bright chartreuse foliage, but it's more difficult to keep looking good.

Aspidistra: This large plant has big leaves that grow from thick, horizontal rhizomes at the soil surface. While it may be hard to find, it's also hard to kill.

Oxalis: Often called shamrock plant, this easy grower has green or burgundy-colored foliage and slender stems of delicate pale pink flowers.

Moth orchid: This tough orchid (Phalaenopsis) has large, leathery leaves that produce thick stems of multiple white, pink, lavender or yellow flowers once or twice a year. Some consider the plants unattractive when not in bloom, but the flowers typically last a whopping two to three months.

Croton: This colorful plant has leathery leaves brightly splotched with red, orange, green and yellow. It requires bright light to keep its colors. Without it, the foliage loses much of its variegation.

Spider plant: This popular green and white trailing plant is well suited to hanging containers. Small plantlets that develop on cascading stems may easily be rooted.

DEB BROWN