What's The Optimum pH Level For Houseplants?

What’s The Optimum pH Level For Houseplants and Why It Matters?

Determinating the optimum pH level for houseplants is highly important if you want to grow a beautiful garden.

I think there is no person in the world who would have something against living in a house full of plants.

Colorful flowers with various scents, those leafy beauties that create a sense of serenity, and even herbs and fruits and vegetables (yes, you can grow some of them indoors).

All of them add vibrancy and life to your home.

So have you ever seen a beautiful flower at your neighbor’s house and tried to grow it yourself but it somehow never blooms, or does not grow as fast or as big as your neighbor’s does?

You probably have, as have I. So, what could be the problem?

Let us think. What does a plant need to thrive?

Many factors come together to enable your plant to grow – some of them are light, watering needs, temperature, nutrients.

You talked to your neighbor and she told you that the flower needs morning light, so you put it on your east window, you water it once a day (as your neighbor does), you obviously share the same climate but your flower still does not bloom…

The only thing left is the soil, or more accurately, the optimum pH level for houseplants.

Like people, plants also have different nutritive needs: some like more calcium, others more potassium or iron.

And what does that have to do with the optimum pH level for houseplants?

The minerals are water-soluble, and the acidity of the soil determines what mineral will be dissolved and available for the plant to take.

What Is The pH Level Of The Soil?

What Is The pH Level Of The Soil?

Generally, the pH level shows if the environment is acidic or alkaline.

Regarding soil, it determines what nutrients will be soluble for the plant to use…

We measure the pH level on a scale of 1 to 14. The soil that has value 7 is neutral; values from 4.5 to 6.5 indicate that the soil is acidic.

Values of less than 4.5 indicate highly acidic soil. If the pH values range from 7.5 to 8.5, the soil is slightly alkaline, and values from 8.5 -14 are highly alkaline.

Every plant has different acid or alkaline needs.

Most of the plants prefer a slightly acidic and neutral environment (pH values from 6.0 to 7.5), so if your soil is in these ranges, you do not have to make any adjustments unless you are attempting to grow plants that are extremely pH sensitive.

If you determine that the soil you would be using is acidic or alkaline, you might want to choose growing plants that thrive in such an environment.

However, if you want to grow a specific type of plant and the soil acidity does not match the plant’s needs you will have to adjust the optimum pH level of the soil for such houseplants.

Growing plants in an unsuitable soil can lead to issues like stunted growth, lack of blooming, discoloration of the leaves, and even drying the leaves edges due to excess of some minerals.

Sometimes there are enough nutrients in the soil but the acidity is not correct, so the plant can’t absorb them.

The other situation is that there are too many nutrients that are dissolved that they become toxic to the plant and can eventually damage it or even kill it.

How Do You Check The pH Level?

How Do You Check The pH Level?

You can check the pH level of the soil in several ways.

First of all, you can purchase a pH meter, using them are the most accurate (accuracy depends on the meter) option, however, it is the most expensive.

If you plan to use it regularly it could be a good choice to get one for yourself and maintain it regularly (recalibrate with recalibration fluid).

The other option for you is getting litmus paper or pH testing set.

They are the cheaper option, but the values can be off by one or even two units. They are really easy to use though.

If you are not looking for accurate values but just a ballpark of the soil’s acidity, and you are ready to make a scientific experiment at home, here is how you can do it.

Do not fret, it is pretty easy, and you can even do it with your children or grandchildren as a science project and chances are that you have the needed ingredients right there in your kitchen.

First of all, try to take a soil sample from around the root of the plant – this is where they get their nutrients.

Fill one cup with soil, and divide it in half. You will now have 2 cups with an equal amount of soil.

Put half a cup of white vinegar into one of the cups. If the mix is forming foam then it is alkaline with values around 8.

If there is no reaction the soil is either acidic or neutral.

Put enough distilled water in the other cup that the water and the soil create mud.

Take two teaspoons of the mud and mix with half a cup of baking soda (dissolved in a little water).

If the foam is formed it means that the soil is acidic with values between 5 and 6.

If in both cases there was no reaction it means that the soil is neutral.

This is not a highly accurate process but it gives you the idea of the condition of the soil.

My advice is, do not use it if you are planning to grow pH sensitive plants though it can be more than enough for more tolerant plants.

How Do You Adjust the Optimum pH Level for Houseplants?

How Do You Fix The pH Level?

The first thing you need to do is ask yourself if there is really need for fixing the soil.

As I already mentioned, most plants like the slightly acidic to a neutral environment.

Even if the environment is not perfect for the acid-loving, or alkaline-loving plants, in neutral rages of the pH level, there are enough right nutrients for the plant to go around.

Changing the soil, if not necessary can be more of a shock to the plant.

It can cause more problems than leaving it the way it is. Plants do not like to be moved around too much, it is their nature.

Of course, you will carefully watch your plants and take note of the changes and progress so you can revisit the idea later if you need to.

If you decide to adjust the pH level of the soil, there are several ways you can do that.

To raise the acidity you can add agricultural sulfur, caustic potash or potassium bicarbonate.

To lower acidity, add agricultural lime, nitric or phosphoric acid during the growing and flowering phases respectively.

Which solution you want to choose depends on the type of soil and the plant’s needs.

You should make the adjustment gradually and carefully. Take into consideration the amount of soil and its type (different types of soil have different nutrients).

You will have to adjust the solution for each pot individually; however, it is much easier making and tracking the adjustment with indoor plants as it is a controlled environment.


1. How do I know the acidity preference of a plant?

The preferred pH values can usually be found on the seed bags. You can always double-check on the internet as well.

2. What affects the soil’s acidity/alkalinity?

Many factors affect the soil’s acidity-Rainfall, acid rains, human factor, degradation of organic compounds, the soil’s type, and so on.

3. What are acid-loving plants?

There are more plants that love acidic soil than those that thrive in alkaline soil. Acid-loving plants are daffodils, hydrangeas, azaleas, camellias, and many more. Succulents, for example, prefer alkaline soil.

Final Thoughts

This is my experience regarding the pH level and my indoor garden. Do you have any suggestions and what is your personal experience? Comment and share with me, I would be happy to hear from you!