Originally Published: December 28, 2012 10:01 p.m.
If you have problems growing houseplants the issue could be not that you're short a couple of good gardening genes, but in where you have put the plants. Light, temperature and humidity have a lot to do with whether a houseplant thrives or dies, and these factors vary from room to room.
Light: This is the most crucial factor when growing plants indoors. All plants require light to manufacture food, but the amount of light needed varies from one plant to another. Most houseplants thrive in moderate to bright rooms, but flowering plants and those with colored leaves usually need higher light levels than plants just with green leaves. A select group of plants, including the ever-popular Chinese evergreen and cast iron plant, tolerate very, very low light levels.
Plants show signs of stress when light levels are too low or too high for their specific requirements. Insufficient light for green-leafed plants will have them looking weak and spindly, while variegated foliage will lose all or part of its markings. Signs of too much light are bleached or wilting leaves on plants like scheffleras, philodendrons, ferns and peperomias. Quick foliage drop can result from a sudden move from bright to low light.
Humidity: Most houseplants originate in tropical or semitropical regions so they are natives to moist air. Many of these plants can adapt to drier air, but they do better when in a humid environment. With insufficient humidity, their leaves can turn dull, papery, and develop brown leaf tips. These symptoms are especially evident during the winter months when we fill our rooms with warmed air.
One solution is to locate plants that need more humid air in the kitchen or bathroom where humidity tends to be higher. Another option is to place a humidifier in the room where you have most of your plants. Group plants together in a humid room and watch every plant in the group perk up and thrive. Another suggestion is to place plants on a shallow waterproof tray of pebbles that is kept partially covered with water. The pebbles provide lots of extra surface area for evaporation. Just make sure the plant roots hover atop these rocks rather than sitting directly in the water. Some gardeners mist plants to raise the humidity level, but I find this ineffective in our arid climate; the water evaporates before it can be beneficial.
Temperature: Houseplants enjoy the same living temperatures as their gardeners do. Most like daytime temperatures ranging from the 60s° to 70s°F, with nights about 10°F cooler. Plants do not like cold or hot temperature extremes. Outside winter temperatures vary greatly and outdoor fluctuations affect indoor plants. Plants on a windowsill can catch cold when temperatures drop really fast. Keep foliage from touching cold windowpanes and provide protection with a heavy curtain or a piece of cardboard placed between the glass and the plant.
Water: Use tepid water and supply enough so that an excess flows through the soil and out the drainage hole in the bottom of the pot. Do not let plants stand for more than a few hours in water collected in the drip saucer. If necessary, use a poultry baster to pull excess water from the saucer.
Most houseplants do best when their soil is kept evenly moist to slightly dry, while cacti and succulents prefer their soil to dry thoroughly between waterings. A generally good guideline is to allow the soil to dry 1/2 to 2 inches below the surface before watering again. Precision is impossible here; the specific plant, size of the container, and conditions in your home have a significant bearing on water requirements.
Houseplants talk to their owners when thirsty. As their leaves lose their sheen they are screaming, "Water Me Please!" I found an accurate moisture meter that also measures soil pH and light for houseplants. A good moisture meter pays for itself in plant health and a gardener's ease of mind.
Plant food: Fertilizer primarily promotes growth and more flowers. Use a water-soluble plant food low in salt and minerals and designed for plants grown in containers. For my houseplants I prefer "Flower Power54," 10-54-10, used at half strength. A successful rule of thumb is to fertilize regularly in spring and summer when plants are actively growing, and to cut back in fall when growth slows.
Free gardening class - Join me on Jan. 5, from 9 to 11 a.m., at Watters Garden Center for "Advanced Landscape Pruning to Success." Not all plants need pruning in the yard, but timing is critical for those that do. Learn these mountain gardening techniques that are sure to make our yards happy, to help them bloom better, and to reduce plant disease this spring. Dress warmly and bring garden shoes; this will be a working demonstration on the landscape here at Watters. See the entire gardening class schedule on my Facebook page at www.facebook.com/watters1815/events.
Until next week, I'll see you in the houseplant room at the garden center.
Throughout the week, Ken Lain is at Watters Garden Center, 1815 W. Iron Springs Road, Prescott, and can be contacted through www.wattersonline.com.