The most beneficial thing you can do for your houseplants is to change their location according to the seasons. Plants need sufficient light throughout the year to photosynthesize their food.
In winter, when there are fewer daylight hours (about 10 hours now in mid-January in the Fresno/Clovis area) and more stormy, cloudy days, houseplants may not be receiving enough light to keep them healthy. Too little light causes plants to become leggy or spindly and leaves to turn light green or yellow. Even though most houseplants become semi-dormant in winter and do not set new flowers or flush new leaves, they can go into serious decline without enough light.
South windows get the most light and at this time of year the sun is lower on the horizon and deciduous trees are bare of leaves, allowing more rays to enter unimpeded by roofs or tree canopies. West-facing windows receive about 60 percent of the light from a south-facing window.
In winter, move your houseplants closer to south or west-facing window. Not right next to the window itself since glass can transmit cold temperatures, but within 3 feet if possible or to a maximum 6 feet from the window.
If moving your plants closer to a natural light source isn’t possible, artificial lighting can supplement natural light and promote photosynthesis. Some fluorescent lights give off a white, cool light that is good for foliage houseplants; ordinary incandescent light bulbs burn hot and do not give off a wide light spectrum; “grow” bulbs or horticultural-type bulbs give off higher levels of light in the blue and red spectrums – just what houseplants need when days are shorter and sunlight is less intense.
Several houseplants – kalanchoe, chrysanthemums, poinsettia, schlumbergera or Christmas cactus – are photoperiodic or sensitive to light duration. They set flowers when daylight hours are short and need regular watering and fertilization during their wintertime bloom season. Other houseplants, even the nearly constantly flowering African violets, need much less water and no fertilizer from December until mid-February when their dormant period ends.
Overwatering and underwatering are major causes of problems with houseplants. Watering cannot be done on a fixed schedule since temperatures and humidity levels inside our homes change with the seasons. Your finger is your best guide to determining when your plants need water. When the top inch of soil is dry in pots 6 inches wide or less – water your plants until some water runs through the drainhole in the bottom of the pot into the saucer.
Water plants in larger pots when the top 2 inches of soil is dry. In winter check moisture levels weekly and plan on watering every 7 to 10 days. In summer, you may need to water your plants every 3 to 4 days.
The potting mediums or soils used for African violets are peat-based and, if not kept consistently moist, will dry out rock hard and become impermeable to water. Soak dry African violets in tepid water in the sink to rewet the potting soil. Orchid barks can hold water for long periods of time. The very popular phalenopsis orchids survive with only a tablespoon or two of water (from one or two melting ice cubes) every week in winter.
Send Elinor Teague plant questions at firstname.lastname@example.org or email@example.com (“plants” in the subject line).