The garden cleanup is complete. The perennials are snuggling under a cozy blanket of mulch. The lawn has had its final fertilizer of the season; new bulbs are tucked in the ground for spring. The garden hoses have been drained and stored, the rain barrel covered. Now, as winter approaches, we find ourselves spending less time in the garden, and more time nesting indoors.

That doesn’t mean that our interest in gardening has waned. For many of us, nurturing instincts now focus on house plants. Winter is the season we see and enjoy them the most, and it’s also the time of year when they most need our attention.

The majority of house plant species originated in tropical or sub-tropical climates, and to thrive, require the light, temperature and humidity those climates provide. This doesn’t mean that you have to turn your home into a hothouse, but you there are a few things you need to know to keep those plants happy and healthy.

House plants are comfortable with the same daytime temperatures we humans prefer, between 65-75 degrees. At night, they like it a bit cooler, around 60-65 degrees. They should be placed well away from heat vents, radiators, wood stoves and cold drafts from open windows and doors. Fluctuating temperatures can cause damage that may not show up for weeks or months.

You may have noticed that your indoor plants seem to do well in steamy bathrooms and kitchens. That’s because with few exceptions, house plants love a humidity level of between 40 and 50 percent. Unfortunately, the relative humidity of most well-insulated, airtight modern homes is around 15-20 percent.

You can increase relative humidity several ways. Using a humidifier is ideal, but there are other simple solutions. Start by grouping the plants together. Moisture evaporating from the soil and leaves creates a humid environment. Tucking an ordinary glass of water between the plants will further boost humidity. Remember to fill the glass when you water the plants.

Another way to increase humidity is to create a pebble tray. Use any waterproof tray-like container, cover the surface with pebbles, small stones or gravel, and fill with water just to the top of the stones. Place potted plants on the stones.

Your plants will enjoy an occasional misting, but don’t rely on this method alone to raise humidity, unless you do it several times daily.

The major cause of house plant problems is overwatering and underwatering. You can tell when the plant wants a drink when the soil is almost dry to the touch. Most house plants require less water during the winter, but when the wood stove or central heating is on, check them frequently to make sure they’re not drying out and adjust watering accordingly. Too-dry conditions may spawn outbreaks of insect pests such as spider mites.

This is the time of year that most plants are resting, not growing, so put the fertilizer away until February. Don’t worry; the plant won’t starve to death if it’s healthy. If you’re a compulsive plant parent and feel you simply must feed, use half-strength liquid fertilizer no more than once a month.

We hear a lot these days about Seasonal Affective Disorder (SAD), which causes some of us humans to exhibit symptoms ranging from lethargy to major depression. Brought on by low light intensity, it is often relieved by the use of full-spectrum lighting and light boxes. House plants may also experience a form of SAD. Adequate light is critical to plant health (especially flowering plants) during the winter months. If plants appear pale and spindly, they may not be getting enough of it. When they start stretching toward the light source, they’re telling you they need more. A plant on a windowsill gets light from one side only, unless you turn it regularly to keep it straight and shapely. This doesn’t apply to Christmas or Easter cacti, which may drop their buds if turned.

You may want to supplement natural lighting with the fluorescent lighting plants enjoy. Be sure to turn it off at night, though. Plants generally don’t do well in continuous light. They need their sleep as much as we do.

House plants occasionally require a bit of house cleaning. Every so often, gently wipe both sides of leaves with a damp cloth to remove dust and grease. Keep pots sanitary by removing dead leaves and other debris.

In the next column we’ll discuss the most common pests and diseases of house plants and how to manage them.

Garden questions or comments? Call 675-6611 or e-mail editor@whidbeynewstimes.com. Mariana Graham is a WSU-certified Master Gardener and a member of Garden Writers Association of America.