WITH COLDER weather coming soon, it's time to bring in your tender tropical plants. You'll need to make some cultural adjustments for the care of your indoor plants once you bring them indoors. Light, temperature, water, nutrition and soil are the main factors affecting plant growth.
LIGHT
Light is necessary to grow healthy plants. Light intensity is measured in foot-candles (fc), and indoor plants are often classified by the amount of light they require:
Low (minimum 25-75 fc, 75-200 preferred for good growth)
Medium (minimum 75-150 fc, 150-500 preferred)
High (minimum 150-1,000 fc, 500-1,000 preferred)
Very high (minimum 1,000 fc, 1,000-plus preferred)
A sunny day will register about 10,000 fc outdoors, while the interior of even well-lighted homes often has less than 100 fc So plants that require very high light will generally not do well inside. Plants that require high intensity should be placed near a window with a southern or western exposure.
Medium light plants can be grown up to several feet away from these light sources or in eastern exposures, while low light plants can be grown several feet away from eastern exposures or in northern exposures.
Artificial light can be used to supplement natural light, but the correct light source must be used. Fluorescent or special incandescent light works best. Standard incandescent bulbs do not provide adequate light. Plants grown under incandescent light tend to get leggy.
TEMPERATURE
Most house plants grow best when daytime temperatures are between 70 and 80 degrees, and 60 to 65 degrees at night. Though many homes fall within this range, remember to not turn your thermostat down too far when you leave for a few days. Most house plants are tropical in origin and can be damaged when temperatures reach 50 degrees.
WATERING
Improper watering can be the most detrimental factor to indoor plant health. How often you should water has no simple answer. Factors such as plant size, container size, soil type, temperature and humidity as well as plant species all apply.
Some plants must be kept moist while others prefer drier conditions. Most people water their plants when the surface appears dry. But this fails to account for roots in the moist lower portion of the container that could be overwatered.
The best way to determine when to water is to push your finger an inch or so below the surface. If it feels moist, do not water. Moisture meters are an option, but they vary widely in accuracy.
Since fertilizer content and soil type can influence the accuracy of moisture meters, having identical readings in different pots does not necessarily mean the same moisture content. The use of drain saucers can also negatively affect plant growth. Letting water sit in the saucer after watering can result in excessive buildup of salts in the soil as well as soil saturation in the lower third of the pot, leading to root rot.
To prevent this problem, excess water should be discarded after watering. To prevent salt buildup, place the plant in a sink and water thoroughly to leach out excess salt once a month.
FERTILIZING
Though all indoor plants need some fertilizer for proper growth, those that have low light requirements generally need less fertilizer. While granular or slow release fertilizers are acceptable forms to use provided they are used at proper rates and intervals, water soluble forms are preferred to reduce the potential for fertilizer burn.
Always read the label to determine the concentration and frequency of application. Most plants will do well with a 1-1-1 ratio fertilizer such as 20-20-20 or 10-10-10. A white, flaky film on the soil surface or pot rim is a visual indication of salt buildup and it should be leached immediately.
SOIL
Most commercially available soil mixes are satisfactory for growing indoor plants. Make sure the soil mix has good water and nutrient holding capacity, provision of good support for the plant, and good drainage and aeration. Common ingredients of professional soil mixes are coarse sand, processed bark, sphagnum peat moss, perlite, vermiculite and leaf mold.
Avoid using native soil, which has a high clay content. If used, it must be amended with compost, sand, perlite or vermiculite to improve physical structure. It will also have to be sterilized to kill weed seeds, insects and disease organisms.
If you would like more information on the care of indoor plants or advice on a house plant that is not doing well, please contact me.