Houseplants Under Lights

Lesson 3: Watering, Humidity and Fertilizing

Fertilizers

Plants need food just like humans. Learning to recognize the signs of too little or too much fertilizer is one of the keys to keeping your houseplant happy.

Every plant needs food to grow. A program of fertilizing is essential for the continued well-being of your plant.

Signs of Needing Fertilizer: The plant quits growing, flowering, or plant stems are weak. Leaves are a lighter shade of green than normal.

Signs of Too Much Fertilizer: The leaves wilt (be sure it doesn't need water first!), flowers wilt or fail to open, leaf tips are burned (crispy looking), growth is stunted or weak, there is a chalky or crusty buildup on outside of clay planters.

What is in Fertilizers?

Three major ingredients are found in every houseplant fertilizer: Nitrogen, Phosphorus, and Potassium. These are essential to the health of your plant. Several micronutrients (which means they are needed only in small amounts) include sulfur, calcium, magnesium, boron, copper, boron, molybdenum, zinc, manganese and chlorine.

Each packaged fertilizer is labeled with a series of 3 numbers, such as: 5-3-7. The numbers stand for nitrogen (N), Phosphorus (P), and Potassium (K). The numbers for the various micronutrients are usually given on the back label. These numbers indicate the percentage of the respective fertilizer contained in the mixture.

Forms of fertilizer

Fertilizers are sold as a dissolvable powder, granules, sticks, and liquids. Every fertilizer, including the liquids, need to be mixed with water before application. Follow the package directions regarding amount of fertilizer and quantity of water to use for a single application. Be sure to not use more than the recommended amount of fertilizer or you may burn the roots of your plants.

How Do You Fertilize? There are several ways to fertilize. Choose one method and stick to it unless your plants indicate that another method is needed.

Choices:

• Mix the fertilizer in water and use this water once a month to water your plants.
• Mix the fertilizer in a spray bottle and fertilize by spraying the plant's foliage. (Don't do this with hairy-leaved plants.)
• Add slow release pellets to the root zone area of the potting media. This will fertilize your plants whenever you water for a set period of time. You can also use the stick fertilizers in the root zone region. Neither of these forms of fertilizer releases their nutrients unless they are in contact with water.
• You can fertilize with a reduced amount of fertilizer each time you water. This is my personal preference since it works well with wicking and is easier than trying to remember when you last thought about fertilizing your plant.

Some plants prefer a potting media that is slightly acidic (has a pH under 6-7). Use one of the fertilizers made for Azaleas, Camellias or Gardenias. If you have a plant that has leaves with green veins and yellow coloration in between the veins, you have a plant that isn't getting the iron it needs. This problem is called chlorosis. This problem results when the potting media is so alkaline that the iron isn't available to the plant.

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