Fertilizer or Soil? Which is Best for My Indoor Plant?

When it comes to indoor plant growth, soil vs. fertilizer has been an ongoing debate before I joined the gardening scene. Some say that fertilizer is not needed if you have good potting soil. Others scoff and disagree.

One thing’s for sure- we’re going to dive further to figure it out!

The Purpose Of Soil

Soil is the epicenter of your plant’s development cycle. Being the service station for PH balancing, energy production,  water filtration, and other key functions, the quality of your soil plays an important role in your plant’s survival.

Through its organic and chemical components, soil can directly transmit its health status through plant roots which then shows itself in how the stalks and leaves look. 

Soil Makeup Is Important

Now depending on the types of plants you own, certain structures have particular needs. For instance, the soil structure for a Geranium plant is relatively less dense than the soil of a tulip plant that needs slightly more acidic soil.

Likewise, for an indoor fiddle leaf fig tree, the soil structure works best with a well-draining mix of peat moss to organic matter instead of an Aloe Vera plant- which doesn’t need soil at all.

Soil Types For Indoor Plants

Although not exclusive, the following list provides a glimpse of the different types of soil mixtures required for various indoor plant types.

Vegetable Containers

Indoor vegetables require a soil ph between 6 to 7, plus a well-draining mix of potassium, vermiculite, perlite, and organic matter.

Herb Containers

Herbs such as Oregano and Parsley require a soil blend of organic matter that consists of peat moss and perlite (possible to add coconut coir and cactus mix) with a ph that ranges between 5-7.

Bulb Containers

Tulips bulbs require a ph range of 6-6.5 with a heavier soil mix of bone meal, organic matter, and sand.

Houseplants That Can Grow Without Soil

• Aloe Vera
• Hyacinths
• Lucky Bamboo
• Spanish Moss
• Orchids

The Role Of Fertilizer For Indoor Plant Growth

As we mentioned, the soil is the plant’s development ‘machine’. And in maintaining this machine, some gardeners choose to incorporate fertilizer to help further growth- while others choose not to touch it.

We’ve gone deeper to figure out why that is and why some are reluctant—and the results were surprising!

Fertilizer Provides Nutrients

Without a doubt, the sole purpose of fertilizer is to provide additional nutrients to the soil to develop plants and crops further. Most commercial fertilizers are composed of potassium, nitrogen, phosphorus, calcium, and iron, but that is not always the case.

Think Popeye and his can of spinach- ‘Popeye’ would be the soil while fertilizer would be the ‘spinach’ that gives Popeye super strength.

The Benefits Of Using Fertilizer

There are many reasons why gardeners choose to utilize fertilizer. For starters, most commercial brand potting soils lack key nutrients to keep your plants healthy and happy.

And should you mistakenly purchase a bag of mix that has been sitting on the shelf for quite some time, it may have little to no nutrients left to truly benefit your container plant.

Next, depending on the type of indoor plant, what’s provided in the potting soil may not be able to keep up with the weekly demands of your plant- thus why you can see your plant shiny and bright one week, and the next drooping and dark.

By incorporating fertilizer, the soil gets that extra kick to supply the roots and stems with what it needs and thus maintains a healthier environment than what the soil could accomplish on its own.

Can Plants Self-Fertilize?

If you’ve done your research and have developed your own particular potting and watering matrix, you probably are already lightyears ahead of what I’m about to say.

Plants are fickle, and depending on the type of system you’ve created; you may have given your plant an environment that no longer needs outside assistance to survive.

Plants can self-fertilize if provided a community where they can pull from many different sources the basic needs of food, water, and fresh air. This can be created by having a diversity of plants, organic covering, and a self-watering system.

By utilizing these three, plants can become self-sufficient as the environment will mimic a natural outdoor cycle and act accordingly.

Soil or Fertilizer- How To Determine Which One To Use?

Going back to our Popeye analogy, plants can grow sturdy and strong with soil alone, while others need its ‘spinach’ to power up. In the case of indoor plants, the following is a list of examples of plants that can survive best without added fertilize:

• Gardenias
• Citrus
• Shrubs

While this indoor group does best with added nutrients (although heavily debated):

• Roses
• Perennials (such as Phlox, Begonias, and Ferns)
• Hydrangeas

Tell-Tale Signs Indoor Plant Soil Has Enough Nutrients

A good tell-tale sign that your soil is providing your plant with what it needs is by looking at the physical health of the plant; when trying to find other signs, we usually look at the following:

• Your plant is growing at a rate on or exceeding the target of what’s recommended.
• Temperature and humidity have been at a consistent level.
• Your plant leaves are not yellowing nor producing a light green color.
• Same with the base of your plant- it is not yellowing or turning a dark purple.
• Your plant has a healthy fragrance and does not smell rancid or producing strong, unusual odors.

If you begin encountering any of these, then it is a sure sign that it may be time to check the soil and add fertilizer.

Also, as an honorable mention, be sure that you are not fertilizing when the plant is dormant or ‘sleep.’

Always research the life cycle of your particular plants and make sure you’re not adding your seasoning to nature’s mix. It may produce the above-mentioned results, which will leave a bigger mess than what you started out with.