With dropping temperatures, the gardener's mind often turns to houseplants. And rightly so.

There are many reasons to grow plants indoors. Plants are beautiful and add a soft touch to a home's design. Healthy plants can also give us a feeling of happiness and purpose. It is reported that plants can help keep the air clean. According to a study by NASA, the recommendation is to have 15 to 18 plants in 6- to 8-inch pots for the average 1,800-square-foot house.

The best way to care for plants is to place them where they are easily accessible. Check on them weekly. Create a routine that reminds you to check your plants on a certain day of the week. Choose plants that are right for your living space, depending on whether it will be hanging from the ceiling or sitting on a windowsill, table or the floor.

The four main types of indoor plants are foliage, flowering, succulent and florist plants. This article will focus on foliage plants.

Now is a good time to repot plants that are in dry compacted soil. Plants that have been brought inside from outdoors may have eggs getting ready to hatch from insects who chose your plant's pot for their habitat. Use fresh potting mix when doing this.

Six environmental factors must be considered in providing good growing conditions for your indoor plants:

- Light - Most houseplants are tropical or subtropical and are native to regions with indirect light. Light intensities inside the home are significantly lower than outdoor light. Plants require certain levels of light depending on the species: either direct (near a window with direct sunlight on the plant), indirect (near a window but behind a sheer curtain), moderate (several feet away from a sunny window) or low (in the middle of a well-lit room with little or no light from outside). It is possible to find light requirements for many popular indoor plants at the following link: www.ext.colostate.edu/ptlk/ptlk1300.html.

- Temperature - Most houseplants prefer temperatures between 65 and 75 degrees Fahrenheit. They tolerate slightly cooler temperatures in winter when they go through a period of dormancy. Drastic temperature swings of 15 degrees or more can be damaging or fatal.

- Humidity - While the average relative humidity in most homes is 15 percent, most indoor plants do best when there is 85 to 95 percent humidity. To raise humidity levels, try any one of the following: use a humidifier, group plants together, place plants in a terrarium or set plants on pebble trays that maintain a water level below the bottom of the pot.

- Water - Too much or not enough water tends to be high on the list when plants are doing poorly. Frequency depends on the environmental conditions mentioned thus far as well as the time of year, type of container, composition of the soil and plant species. Most indoor plants like to dry out slightly between waterings. If the top of the soil is dry, it may be time to water. It is essential that your indoor plants are allowed to drain excess water into a tray. This will prevent the pore space in the soil from becoming waterlogged, which can cause root rot. Any water remaining in the tray after 30 minutes should be discarded.

- Fertilizer - Indoor plants should be fertilized on a regular basis from March to September. Using a complete houseplant fertilizer containing nitrogen, phosphorous and potassium is usually sufficient. When using water-soluble solutions, it is best to fertilize often at low concentrations rather than infrequently at high concentrations, which may lead to root or leaf damage. Try mixing according to the product directions but at 1/4 strength, and use weekly. Slow-release granules can also be found at the garden center.

- Soil - The medium in which a plant is potted varies. Cacti and orchids have their own special mixes. The average indoor plant requires a well-draining mix that holds water and nutrients, provides pore space for oxygen and is stable enough to keep the plant from toppling over.

Two main categories include soil-based and peat-moss-based. There are advantages and disadvantages to both, and the choice is often based on consumer preference.


Get answers to your horticulture questions by calling a master gardener volunteer at 520-7684 or emailing CSUmg2@elpasoco.com.