Houseplant Basics 101-Fertilizer

All houseplants need fertilizer to supplement their diets. Think of it as a good shot of vitamins and minerals. Although your houseplants feed on light and the nutrients in the soil, a boost of fertilizer can help to promote and support strong, healthy growth.

Fertilizers contain three major nutrients to support stem and leaf production, flowering and healthy roots. These elements are nitrogen (N), phosphorus (P) and potassium (K). Whenever you look at a container of fertilizer, pay close attention to the fertilizer analysis which is represented by three hyphenated numbers. For example, it may look something like this: 20-20-20 or 10-6-16, or 10-15-10 like on this bottle of “SCHULTZ” LIQUID PLANT FOOD PLUS . The first number always represents the available nitrogen in the fertilizer. The second number always represents the available phosphate and the third number always represents the available potash in the fertilizer. The higher the number, the greater the percentage by weight of that nutrient.

Houseplants require nitrogen for leafy growth. As a general rule, houseplants that are grown primarily for their foliage will require a fertilizer with a high first number, a lower second number and a third number that is comparable to the first. Houseplants that are grown primarily for their blooms are given a fertilizer with a high third number (K or potash) that promotes flower development.

Fertilizers are most beneficial to a plant during its growing season, which is February to October. During the winter months when there is less light, you will want to hold back on fertilizing unless your houseplant is beginning to show signs of new growth. Your houseplant’s consumption of fertilizer will follow its growth curve, which in turn follows a light and temperature curve.

General Rules for Fertilizing

  • Granular and liquid fertilizers work similarly. Be sure to read the instructions and mix and feed accordingly.

  • Hold off fertilizing for at least a few weeks after houseplants are repotted. It isn’t that your houseplant doesn’t need food; it is that they only need so much. Most soils contain unknown amounts of fertilizers and it is easy to overfeed your transplant.

  • Water until water flows out the bottom of the container. This step will flush out any built up soluble salt deposits. As salts become more concentrated, it becomes harder for a houseplant to take up a proper supply of water.

What is your favorite fertilizer to use in your houseplants? Leave me a comment and share.