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Indoor plants.

Plants kept in homes, offices and other indoor locales brighten the space, clean the air and generally make the people around them feel better. Indoor plants can be especially welcoming in the short, dreary days of winter. Satisfaction with them depends a lot on the health of the plant, though, and success in keeping them alive takes a little awareness of and response to plant needs.

All plants need light, water, air and nutrients. How much of each of these things they need is dependent on species and ability to adapt to the local environment. For example, some plants may thrive in a variety of light conditions, but need a little time to adapt when moved. This is most evident when bringing a plant home from the greenhouse or moving it inside after being outdoors all summer.

Light

Light quality in homes and offices is very filtered compared to outdoors, even in shady locations. Very few plants can survive away from a window or other natural light source, so avoid keeping plants on a desk or other location away from windows unless the species is noted for being able to survive such conditions.

Plants that lean or stretch toward light sources want more light. Move them to a brighter place if possible. They can also be rotated regularly so that the plant grows evenly, although some experts recommend against it because it stresses the plant.

When purchasing new indoor plants, look at light requirements carefully. Plants labeled as needing bright direct light need the most light and should be kept in south- or west-facing windows with lots of exposure. Indirect light means an east window or one that is a bit shaded. Even plants with low light requirements perform best near a window or other natural light source.

Water

The rule to watering indoor plants is: It depends. Plants are more likely to suffer from overwatering than underwatering, especially in the winter months, so try to err on the side of neglecting them. Stick your finger into the soil to check for moisture before watering and if the soil is still moist below the surface, wait a few more days.

Water from the tap in your home probably contains salts that can be harmful to the plant if they build up in the soil. Some plant species are more sensitive to this than others. One way to at least partially avoid this is to apply water until it flows out the bottom of the pot. That means keeping a saucer under the pot or setting it in a sink or bathtub every time. If the pot the plant is growing in does not have a hole in the bottom, transplant it into one that does or drill holes into the pot so it can drain.

Room-temperature water is better than very cold or hot water that can shock the plant. Try filling the watering can or container with water the day before you plan to water to allow water temperature to adjust. This also allows some of the salts to dissipate. Bad at planning ahead? Fill the watering can each time you empty it and let it sit near the plants, so it is ready to go next time you are ready to water.

Air

Plants take in carbon dioxide, which humans release when they breathe. There is an ample supply in the atmosphere, luckily. Moisture in the air is sometimes a concern — most plants benefit from a little humidity. Some references recommend misting plants or setting a tray of water nearby. Neither of these practices has been shown to make a difference in plant health. A humidifier can help but may not be justified just for the plants.

Nutrients

Commercial potting mixes contain everything indoor plants need, so freshly potted and repotted plants have enough nutrients in the soil in which they are growing. Over time, nutrients deplete and need to be replaced. Look for a fertilizer labeled for houseplants as it will give you the best instructions on how much to use and how often to use it. There are many different formulas available.

Avoid fertilizing indoor plants in winter since they are mostly surviving right now. Wait until days lengthen and warm, when plants are growing more rapidly.

Other

Most indoor plants prefer temperatures in the 70s during the day and 60s at night. Warmer and colder temperatures can stress plants. Also, avoid placing plants where they will catch drafts from opening and closing doors or from heating and air conditioning vents.

Soil is something many people think is essential to plant growth, but it is not. Soil provides support for plant roots, insulates roots from drying and holds water and nutrients for roots to uptake. Most indoor plants benefit from being grown in potting mix or potting soil specially formulated for their growth. These commercial mixes are made from peat and composted bark and provide much better drainage than regular garden soil.

Occasionally potting mix/soil should be replaced in a process called repotting. Avoid repotting now, but consider performing this task in late winter or early spring for plants that need it.

• Jennifer Smith is a former horticulture extension agent for K-State Research and Extension and horticulturist for Lawrence Parks and Recreation.