How to Fertilize House Plants

Having plants in your house or apartment is a great way to brighten up your home and bring a little bit of the outdoors inside.

To keep your plants happy and healthy, you’ll need not only to provide them with the appropriate amount of sunlight and water, you’ll also need to fertilize them regularly.

Choosing a Fertilizer

Figuring out which fertilizer to buy can be confusing, since there are virtually dozens of different fertilizers available at most hardware and garden stores.

Types of Fertilizer

House plant fertilizers can usually be found in three different types:

  1. Time release fertilizer spikes: These are placed in the plant’s soil and will release fertilizer with each watering. The spikes last for several months and may be a good choice for those who are apt to forget to fertilize their plants
  2. Liquid fertilizers: Dilute these fertilizers with water and then use the mixture to water your plants
  3. Water soluble fertilizers: These come in powder or granule form and should be fully dissolved in water before they are fed to plants

The type of fertilizer you choose does not make a big difference and is based mainly on personal preference and price. All three types, when used correctly, will deliver the necessary nutrients to your plants.

Fertilizer Formulas

All plant fertilizers contain three nutrients essential to plant growth: Nitrogen, phosphorus and potassium. The percentage amounts of the three main nutrients will be advertised in this order on the product label.

For example, a fertilizer that’s formula is listed as 8-7-6 contains 8% nitrogen, 7% phosphorous and 6% potassium. Trace amounts of other elements, nutrients and minerals are also included in most fertilizers.

The three main nutrients are each responsible for different elements of plant growth:

  1. Nitrogen promotes the growth of healthy leaves
  2. Phosphorous promotes healthy roots and encourages flowering plants to bloom
  3. Potassium promotes stem strength and helps plants remain healthy during periods of dormancy

The type of plants you have will determine what formula of fertilizer you should buy. If all or most of your plants are non-flowering, your best bet is to purchase a fertilizer that is high in nitrogen. If you favor flowering plants, you’ll want to choose a fertilizer that is high in phosphorous.

If, however, you have a mix of green and flowering plants, it is not necessary to buy separate fertilizers, although you can do so if you wish. A fertilizer that has relatively equal amounts of each nutrient, such as a 20-20-20 or 8-7-6 will be suitable for use on all your plants.

When to Fertilize

Plants only need fertilizing during periods of active growth and should not be fertilized during periods of dormancy. Most house plants will be active during the early to mid-spring until late fall. Therefore, you should only fertilize your plants from about April until October. Plants that have been recently purchased or repotted do not need to be fertilized immediately, as there should be a sufficient amount of nutrients in the potting soil to last them for several months.

Most fertilizers will contain instructions directly on the product label and usually recommend that you fertilize once per month. To ensure that your plants are provided with constant nutrients, some experts recommend that you fertilize less, but do so more often. For example, if the product label recommends that you add one tablespoon of fertilizer per liter of water for monthly applications, use one quarter of a tablespoon of fertilizer for each liter of water and apply it weekly.