Should You Fertilize Houseplants? – The Verdict Explained


Looking at some houseplant tags recently I must admit they were somewhat confusing.

It’s easy to understand why houseplants have problems indoors – If you follow the directions on the plant tag.

One tag said – “Fertilize Regularly”.

What does “Fertilize Regularly” mean?

  • Every Day
  • Three times a day
  • Once per week
  • Once per month
  • Once per year

Let me briefly explain some things about buying house plants, fertilizer and why I would recommend to you – not to fertilize your indoor plants.

Fertilizer & Plant Food in the Nursery

When a plant grows in the nursery it receives higher light and produces food to fuel its growth. It needs fertilizer regularly to support itself. When the houseplant moves indoors this process slows down (greatly).

Most of the time we see nutritional deficiencies when the plant is actively growing in the nursery, when it needs more food or does not have enough of a particular element, such as iron, leaves may turn pale.

We also see deficiencies when plants flower. The flowering process may use up specific elements causing a deficiency to show up in the leaves.

Many growers today use time release fertilizers to feed plants regularly. Growers try to time crops so plants are shipped with fertilizer activity is on the down side.

If you look on top of the soil of most plants you may notice some prills gray or golden in color. This is usually time release fertilizer.

Growers “should” remove most of the plant fertilizer off the top of the soil before shipping. The plant should still have plenty of fertilizer in the soil to sustain it for a long time.

Plant Fertilizer Explained – Salts Burn!

Fertilizers are basically salts. If you took a bag of fertilizer for grass and dump it into a pile on your grass, the grass would burn because of the salts. This is not a case of – “A little bit of fertilizer is good and a little more is better”.

If you were to take that same lawn fertilizer and mix it with 10,000 gals of water then poured the fertilizer on the grass the salts would be diluted and you wouldn’t or shouldn’t have a burn. Even liquid fertilizers can burn including natural!

What Happens with Fertilizers in a Pot?

When you fertilize in a pot you put in salts. If the salts are not leached out (through watering), they remain in the pot. Over a period of time salts can build up and burn the roots.

If you over fertilize, as it is easy to do with liquid or solid fertilizers the situation is easily multiplied.

Have you ever noticed the white stains on clay pots? Or have you ever heard of soaking a clay pot in water before reusing the pot? The reason for soaking the pot is to leach the salts out of the pot.

Most of the fertilizer used for house plants comes in liquid form. If you’re going to fertilize plants indoor – cut the dose.

The question is: How much fertilizer to use on plants? You could probably cut the recommended fertilizer rate of 1 teaspoon per gallon to 1/5 or 1/6 of a teaspoon per gallon.

Leaching the Soil of Salts

The next issue becomes – leaching. In order to leach the potting soil media plant of salts you must add more water.

Then, we run into the problem of overwatering… all the more reason to look at sub-irrigation or self watering planters as a plant care solution!

It all ends up with additional “other problems” or potential problems.

Our focus on fertilizing is on your indoor plants, your outdoor or patio plants is another issue along with African Violet Care. The African violet can probably be feed regularly but that is another topic at another time.

Back to the Tag…

Is there ever a time to fertilize your indoor plants? Yes, but very rarely. The tag said to fertilize regularly, and I would agree. Fertilizer your indoor plant once every 5 years, but do it regularly.

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