Fertilizing for Houseplants (5607)

Foliage plants that come directly from Florida often arrive with high fertilizer levels in the soil. Florida growers feed regularly and at a fairly high dosage to make plants grow. This is fine in areas where there is high light intensity and plants are watered daily.

However, indoor conditions are quite different here. You may water plants only once every three or four days due to low light conditions. Higher fertilizer levels soon begin to injure the root system and plants may decline.

A standard recommendation calls for a heavy watering of plants shipped directly from Florida to northern homes. This process is called leaching. It is important to reduce excess soluble salts to avoid injury to the plant’s root system.

Do not feed most plants for the first three months after they arrive in your home. This is especially important for those plants that come directly from Florida. Northern grown plants often have sufficient nutrient supplies to last approximately two to three months. Ask the retailer whether plants came directly from Florida or if they spent time in northern greenhouses.

It is always a temptation to feed plants when foliage begins to turn yellow. The real problem may be one of excess soluble salts or fertilizers in the soil. Water the soil heavily to remove toxic salts.

Look at small and medium plants before you fertilize. Simply remove the soil ball from the pot and examine the root system. The appearance of white, healthy roots surrounding the soil ball suggests there are no excess salts in the soil. A general lightening in color of the foliage and production of smaller leaves may indicate that you need to start a feeding program.

There are several ways to fertilize indoor plants. Slow-release fertilizers are easy to use; you can buy tablets or small granules to spread on the soil surface. Follow the manufacturer's directions. These fertilizers generally last three to four months.

Liquid fertilizers are a second. The manufacturer may recommend the application of a small amount with each watering. An alternative may be to feed every week, two weeks, or month with a higher concentration of fertilizer.

Feed indoor green plants regularly when they are actively growing. This generally coincides with late spring, summer, and early fall months. Light intensity (how bright light is) plays an important role when you grow plants indoors.

Apply fertilizers when the soil is moderately moist. You can easily injure the root system if you fertilize an overly dry soil ball.

The type of soil mix also influences how often you must feed/water your plants. An increasing number of growers have turned to artificial soil mixes. These mixes contain large percentages of peat moss, vermiculite and perlite. Nutrients disappear from the soil mix when you water frequently and heavily. It is important for you to feed on a regular basis to sustain healthy foliage.

Look at the root systems to help guide your decision whether or not to fertilize indoor plants. Do not apply a fertilizer if the roots are not a healthy white. If you do, the root system may become even worse.

For more information on this subject, Please visit the College of Agricultural Sciences Publications Web site.

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