Light is probably the most important factor for indoor plant growth. In most houses, it's probably the most limiting factor as well. To add to the problem, light levels begin to dwindle in fall as the days become shorter. This means you may need to make some adjustments in the arrangement of your indoor plants during fall and winter.

When thinking about light levels for indoor plants, consider light intensity, duration and quality. Light intensity influences the manufacture of plant food, stem length, leaf color and flowering. For example, a plant that needs bright light that is grown in low light tends to be spindly with light green leaves. A similar plant grown in bright light would generally be shorter, better branched and have longer, darker green leaves.

The distance the plant is from the light source and the direction the windows in a home face determine the light intensity a houseplant receives. Southern exposures have the most intense light. Western and eastern exposures receive about 60 percent of the intensity of southern exposures, while northern exposures get only 20 percent of the light of southern exposures. Light intensity is also affected by the presence and type of curtains, the weather, shade from buildings or trees, the cleanliness of the windows and the reflectiveness of the surroundings.

When a plant gets too much direct light, the leaves become pale, sometimes sunburn, turn brown and die. During the summer, houseplants need to be protected from too much direct sunlight.

Ivy plants, philodendrons, foliage begonias and peperomias - grown mainly for their foliage - do well in indirect bright light. Tender plants, such as African violets, also should receive indirect light during the summer when the sun's rays are extremely intense.

Flowering plants require higher light levels for the development of good flowers. These plants grow best where they receive direct sunlight for at least half a day. Placing them near windows with an eastern exposure usually suits them best.

Here are some suggestions of houseplants for various light situations taken from the UC Master Gardener Handbook.

Low Light Plants

Common Name	Botanical Name
Corn Plant	Dracaena fragrans
Parlor Palm	Chamaedora elegans
Pothos*	Epipremnum aureum
Snake Plant	Sansevieria trifasciata

  Medium Light Plants 

Spider plant. (pxfuel.com)

Common Name	Botanical Name
Peperomia (species)	Peperomia or Pellionia
Rubber Plant	Ficus elastica
Schefflera	Schefflera actinophylla
Swedish Ivy/Creeping Charlie	Plectranthus australis

Bright Light

Common Name	Botanical Name
Christmas Cactus	Schlumbergia bridgesii
Spider Plant	Chlorophytum comosum
String of Hearts	Ceropegia woodii
Zebra Plant	Aphelandra squarrosa

*These plants are poisonous, keep away from kids and pets.

Ed Perry is the emeritus Environmental Horticultural Advisor for University of California Cooperative Extension (UCCE) in Stanislaus County where he worked for over 30 years.

 

 

Your outdoor garden plants may not need a lot of attention on these cold winter days, but have you taken a close look at your indoor plants recently? A house plant with brown leaf tips, wilted leaves, lower leaves that are dropping and little or no new growth may be in trouble. All of those problems, and even plant death, can be caused by soluble salts. 

Soluble salts are naturally occurring minerals, such as sodium, chloride, boron, calcium, and magnesium, that are dissolved in water. Some of the water in Stanislaus County has relatively high levels of certain salts, but in general, all water has some salt. Fertilizer dissolved in water also turns into a soluble salt. After water evaporates from the potting soil, the salts stay behind. Eventually, an excessive amount of salt may be absorbed by the roots, move  upward in the plant, and concentrate in the leaves, causing tip burn. As salts in the soil become more concentrated, plants find it harder and harder to take up water. If enough salt accumulates in the soil, the water absorbing root tips are killed, and the plant begins to wilt and drop leaves.

To combat this problem, be sure you water correctly. Water plants enough so that some water moves through the soil and out the pot's drain hole. Then empty the drip plate. Do not allow the pot to sit in water. If drained water is reabsorbed by the soil, the salts that were washed away are taken back into the soil. The process of removing soil salts is called “leaching.”

It's a good idea to leach your house plants every two or three months. To do this, water the soil thoroughly, as you usually would. Then, after about five minutes, water again, letting excess water flow out the bottom drain holes. The first watering dissolves the salts, and the second washes the salts out of the soil.

As water evaporates from the soil surface, some of the salts may form a layer on the soil surface. If a layer of salts has formed a crust on top of the soil, be sure to remove the salt crust before you start to leach. You should only need to remove about an inch of soil to remove the salt crust. Also, clay pots can absorb salts. If the pot is coated with a white salt residue, it's best to replant in a clean container. 

For more information, consult the UC IPM Pest Notes: Houseplant Problems.

Ed Perry is the emeritus Environmental Horticultural Advisor for University of California Cooperative Extension (UCCE) in Stanislaus County where he worked for over 30 years.

When you think of traditional plants that represent the Christmas season, the poinsettia automatically comes to mind. Other plants also can be used indoors to provide seasonal color, including the cyclamen. With its striking red and white flowers, the cyclamen makes quite an impact, especially when placed around taller poinsettias. In order to look its best during this season, the cyclamen must be given proper care.

You should place cyclamen in a cool, well-lighted area, but not in direct sunlight. An ideal exposure is an east window where the plant does not touch the glass, and where temperatures are 50 degrees F at night and 60 to 65 degrees F during the day. Cyclamen requires moist soil and good drainage. When watering, use lukewarm water, taking care to keep the water off the foliage and crown of the plant. Don't allow the plant to stand in water for very long, as the roots may rot. You can keep the plant from standing in water by placing gravel or broken pieces of pottery in the tray beneath the pot. The plant should be watered so that the soil is not washed from around the corm (bulb-like structure) and roots. 

In the late winter and early spring the older flowers will fade and new flower buds will continue to open, until about the first part of February. At this time, the leaves may start to turn brown, no more flowers will appear, and the plant will seem to deteriorate. If you want to carry the plant over to another season, you'll need to give it a rest period. Do this by reducing the amount and frequency of watering, and by placing the plant in a cool area (40-50 degree F.) until warm, spring weather arrives. At this time you can replant the corm in a well-drained soil mix.

After danger of frost is over, place the cyclamen in a cool, protected location outdoors. Give the plant adequate water and fertilize it about once a month, or less, with a water-soluble fertilizer. During the brightest days of summer, select a location that provides partial shade for the plant to grow. Take the plant indoors before frost in the fall.  

During late fall and throughout the winter, place the plant in full sun (east exposure), with temperatures no higher than 65 degrees F. If everything goes right, your cyclamen should be blooming between mid-November and early December.

Other plants appearing during the holidays include the amaryllis, azalea, African violet, Christmas pepper, chrysanthemum, Christmas cactus, kalanchoe, and paperwhite narcissus, all of which flourish beautifully as houseplants.  Proper care varies with species, but there are some general recommendations to follow when caring for these plants.  Most species do best in a location where as much natural light as possible is available, such as a sunny window. Optimal temperatures include a daytime temperature of 65 to 75 degrees F, and temperatures around 50 to 55 degrees F during the night. An exception is paperwhite narcissus, which holds up better at 60 to 65 degrees F during the daytime, and 50 degrees F at night. African violets and poinsettias prefer even warmer nighttime temperatures, around 60 degrees F. 

Because most homes are extremely dry compared to the greenhouse environment where they were grown, it's a good idea to place the plants in groups or on trays with water. To help prolong the flowering period, you can even place the plants in rooms with higher humidity, such as the kitchen. Usually, however, the plants should be kept in a cooler room, away from warm air currents. Check your plants daily and watered them as needed. Apply enough water each time so that some will drain out the bottom, but be careful not to let the plants stand in water for very long. 

Ed Perry is the emeritus Environmental Horticultural Advisor for University of California Cooperative Extension (UCCE) in Stanislaus County where he worked for over 30 years.