One of the top Google searches on the subject “houseplants” is “fertilizing for houseplants”.   We thought we would share information on this topic. Fertilizing your houseplants is not challenging to do the difficulty is to remember to do it and how to get started.

First, we want to clarify that plants get their food from the sun. They also need other nutrients that they can get from other sources such as soil but houseplants do not get microbes like outdoor plants, so they need some assistance.  Fertilizer should be thought of like a multi-vitamin for plants; but if your houseplant is not in good health, a fertilizer can do more harm than good.

Houseplants need to be fertilized during the growing season.  If you live in the northeast, your growing season would be spring, summer, and fall. In the winter the plants go dormant.  If you live in a more tropical location such as Florida, your growing season would be all year long. When the growing season is just getting started, go easy on the fertilizer.  In the summer you would fertilize more and go back to less in the fall.  How often you need to fertilize will depend on the type of houseplant you are growing.

Types Of Fertilizers

Liquid Fertilizer – these fertilizers are found in organic or synthetic varieties.  They are very easy to use because you can add them to water.

Foliar Spray – this type of fertilizer is useful for air plants. With this type of fertilizer, you would spray it directly on the leaves and not put it in the soil.  Your houseplant takes nutrients through the leaf much faster than it does through the root or the stem.

Granular Fertilizer – this fertilizer comes in different formats. With water-soluble ones all you need to do is add water to dissolve the fertilizer and then you can feed your houseplants. There are granular sticks, which get inserted into the soil near the stem. They eventually dissolve, so the plant can absorb them over time.  This type of fertilizer comes in organic and synthetic varieties.

Soil Amendments – this type of product is not really a fertilizer because it does not guarantee a percentage of elements (nitrogen, phosphorus, and potassium) or other nutrients.  You will find products under this category that have other nutrients such as eggshells and worm compost.  These products are available in organic and synthetic varieties. Be careful of just using some of these organic amendments as they can attract fungus gnats.

What Do The Numbers On A Fertilizer’s Package Mean?

The numbers on the bottle or package of fertilizer are ratios and stand for the percentage of Nitrogen (N), Phosphorus (P), and Potassium (K) macronutrients by weight of the solution they are in. If you see a bottle with 10-10-10, this means it is an evenly balanced solution.  The rest of the ingredients in the solution are just filler. This is one reason that people go with granular fertilizer, so they are not paying for fillers such as water. 

Organic vs Synthetic Fertilizer

Organic means the product is coming from organic sources.  A synthetic solution is manufactured in the lab.  A synthetic solution can be more concentrated.  If you see 20-20-20, these are high numbers, so the solution is synthetic.  Organic fertilizers have smaller ratios of Nitrogen, Phosphorus, and Potassium.  Organic fertilizers are considered gentle fertilizers.  There are also special plant foods for cactus and succulents where you will find the Nitrogen numbers are lower compared to the Phosphorus and Potassium.  Some of the ratios for cactus and succulents are 2-4-7 or 1-2-2.   Orchid and African Violet fertilizer have higher levels of Phosphorus and a ratio for these plants is 1-3-1.

A rule of thumb with synthetic fertilizers is to cut the formula in half because they are so concentrated. It is really easy to over-fertilize your plants, and they really don’t need the nutrients. Organic fertilizers have lower nutrients, so you can use them as recommended.

Fertilizer For Different Types Of Plants

Fertilizers that have a higher ratio of Nitrogen are used to encourage the growth of foliage.  Fertilizers that are rich in Phosphorus are used to encourage the flowering of a plant and root development.  A fertilizer that has a larger ratio of Potassium will help the plant during the dormant period.  A fertilizer labeled 16-5-11 would be good for leaf development and would be recommended for foliage houseplants, while flowering houseplants look for a product plentiful in phosphorus, such as 11-35-15.

Always remember less is more! Too much will burn the plant.

Next week we will have more on this topic focusing on how much fertilizer do I need, how to fertilize your plants, which is better organic or synthetic fertilizer, and more!

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