Many home gardeners enjoy growing plants indoors as well as outdoors. Maintaining the health of plants inside thru the winter time can be a challenge. There are five main factors that contribute to keeping plants happy indoors; soil moisture, light, temperature, humidity, and nutrients.
House plants are probably killed or injured more by improper watering than by any other single factor. Never water any plant unless it needs it. Symptoms of plants that are too dry or too wet are the same. Soil kept either too wet or too dry causes plant roots to die, which leads to poor growth, wilting, or death of the plant. Never allow plants to wilt, and never allow them to stand in water for long periods of time. Learn to gauge the moisture content of the soil by its color and feel. As the soil surface dries it becomes lighter and dry to the touch. Under continued drying the soil begins to crack and pull away from the sides of the pot. When severe drying occurs some damage already will have been done to the roots. It’s usually time to water when the soil surface becomes dry. Because of low light, low temperatures and slower growth, plants need water less often in the winter.
When you water, wet the entire soil mass, not just the top inch. Add water until it comes through the drainage hole in the bottom of the pot. Discard water that remains beneath the pot one hour after watering.
The amount of light necessary for good growth varies with different types of plants. Plants kept continuously in poor light will have spindly shoots, few flowers, yellow foliage, poor flower color and often little or no growth.
Flowering plants need moderately bright light. South, east or west windows are excellent for most flowering potted plants, with the possible exception of African Violets and related plants which prefer a north window. Direct sunlight may cause flowers to over heat and collapse more quickly.
Light at a north window, daylight with little or no direct sun, or sunlight diffused through a lightweight curtain are suitable for most foliage plants. Plants that require full sunlight should be put in a south window.
Fluorescent lights will improve growth when plants cannot be placed close to windows. Place them about 6‑12 inches above the top of the plant, and keep them on for about 16 hours each day. Extra fertilizer, water or repotting are not cures for insufficient light.
Abrupt change from a location in low light to one in bright light may be damaging. Moving abruptly to more intense light may result in bleaching or burning of foliage, especially in direct sun. Any changes should be made gradually. Many plants can be kept from getting one‑sided by turning them once a week.
Proper temperatures for plants are often hard to find in the house. Flowering potted plants should receive temperatures from 65 to 75 degrees F in the day and 55 to 60 degrees F at night.
Foliage plants are more tolerant of high temperatures, but they thrive at temperatures between 65 and 70 degrees.
In winter, plants placed close to a window may have cooler temperatures than that elsewhere in the house. If the drapes are drawn behind these plants at night, the window temperature may be too cool. On cold nights, check temperatures close to windows. Some tropical foliage plants can be injured at temperatures below 40 degrees F.
Do not put plants at windows that have hot air registers or radiators directly below or above them. Hot air blowing on the plants often causes leaves to brown on the edges and occasionally to drop or die.
Air in most modern homes is extremely dry during the winter. A room humidifier can help plant growth. Watertight trays, filled with moist sand or gravel and placed beneath the plants will help increase humidity around the plants. Pots must be placed on top of, not in, the wet sand or gravel.
Fertilizing once a month is usually adequate for most house plants that are producing new growth or flowers. During mid‑winter (December, January) when no new growth is apparent, fertilizer should be withheld.
Do not use fertilizer to stimulate new growth on a plant located in poor growing conditions. Lack of growth is more often due to improper light or watering than to nutritional deficiencies. In such cases adding fertilizer may actually cause additional injury.
Water soluble fertilizers have been formulated for house plants and are available from many garden shops. Follow the directions carefully. The roots of potted plants are easily
burned by the application of too much fertilizer. Never apply fertilizers to wilted plants. Water the plant first, and apply fertilizer after the plant has recovered.