Can Cement Harm Plants? Yes! Here’s How


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In today’s world, cement is mostly used to construct homes, buildings, and other such things. 

Plants can easily become victims of the harmful effects of concrete as we interact with cement when mixing concrete for our DIY repairs at home and through other indirect means such as when they are planted in concrete planters. 

Plants are affected by cement and concrete because the limestone (calcium carbonate) it contains can directly affect the pH of soil, increasing its pH to high alkaline levels. This increase in pH reduces the solubility of the minerals in the soil making it less available for plants to absorb. 

Many people often think that cement and concrete are two same things. However, the reality is, they are different. Cement is a vital ingredient that makes up concrete.

Acid rain can be hazardous for areas where cement and concrete are used because it is responsible for dissolving the cement due to the presence of weak acids in it. 

Let us figure out all the aspects of cement and plants to get a detailed idea about this topic.

In this article, we will be going to cover all the aspects regarding this subject. For the ease of our readers, we have divided the article into the following sections:

  • Can Cement harm plants?
  • What chemicals does cement contain? 
  • Can I mix cement with soil? 
  • How will cement affect soil acidity?
  • Can concrete leach chemicals into the soil?
  • Managing concrete or cement spills on the lawn
  • pH and plant growth
  • Is concrete safe for vegetable gardens?
  • How to make my vegetable garden safe from concrete
  • Can you plant on concrete

Can Cement Harm Plants?

Cement on Soil

You might get surprised by nature’s phenomenon regarding soil pH levels. It indicates the nutritional ability of soil, and it determines the number of nutrients that the plant could get from that soil. 

It is the reason behind many theories that indicate only a particular type of soil is eligible for the growth of some specific plants. 

So, the pH level must be maintained for the healthy growth of plants, and if the pH level gets disturbed, it can badly affect the growth of your plants.

The presence of cement in the soil can increase the pH level of the soil due to the presence of different chemicals.

It is not necessary to add cement into the soil to increase its pH level but, if you are using a cement-made pot, acidic rain can mix it with soil and let the chemical reaction take place. 

Therefore, we can say, cement can harm plants by increasing the pH level of the soil and hence decreasing its nutritional abilities. 

Therefore, it is better to grow plants in clay pots or in the area where there is no usage of cement so that plants can grow without harmful chemicals in the soil. 

To test the moisture and pH of the soil you can use the cost-effective Trazon Soil 3-in-1 Meter. It not only tests for pH but also moisture content and light intensity. You can find it by clicking here!

Trazon Soil pH Meter 3-in-1 Soil Tester Moisture

What Chemicals is Cement Made up of?

Concrete Planters

Cement is composed after the mixing of multiple types of chemicals. The chemical reaction that takes place after the mixing of those chemicals will, in turn, compose cement, which is then used for construction purposes. 

The chemicals included in cement are calcium, silicon, aluminum, iron oxide, sulfate, silicon dioxide, calcium oxide, belite, alite, potassium oxide and sodium oxide.

All of these chemicals have different properties like some are responsible for reducing the melting temperature, some are responsible for the slow hardening process, and so on.

Cement is typically used as a binder during the construction process, and it hardens and adheres to other materials that are responsible for the construction process. 

It can’t be used alone for the construction because, as we discussed earlier, it is mostly used only as a binding agent.

However, without it, it is nearly impossible to mix up different things that are responsible for constructing a building or a house. 

However, due to the presence of many harmful chemicals in the cement, it is highly toxic for the eyes, skin, and respiration.

Many people around the globe are allergic to cement as the chemicals involved in its production are responsible for these side effects. 

Can I Mix Cement with Soil? 

If we only talk about the general mixing of cement and soil for the construction process, then we can say yes, it does happen. 

Cement has an adverse effect on the nutritional efficiency of soil because it badly affects the pH level of the soil. 

Thus, that kind of mixture can only be used for construction purposes and not for plants or crop production. 

The reason behind not using this mixture for planting is the presence of lime in the production of cement. It can leach into the soil, and in turn, increase the pH level of the soil. 

There are many plants that can only grow in only a soil-based medium or one mixed with a small amount of amendments like perlite or vermiculite, and the absence of those natural conditions can kill them. 

Therefore, if you wish to grow a plant in the soil that is mixed with cement, it will be of little success. It is something that a person can never overlook if he wishes to grow the plants. 

How will it Affect Soil?

Cement has an alkaline nature. By alkaline, we mean a higher pH level. A normal pH level for plants is slightly acidic ranging between a pH of 6.5 to 7. 

However, cement is alkaline in nature which means that it has a pH level higher than seven. 

This nature of cement is due to the presence of multiple chemicals in it, and if we mix it with soil, then it has the ability to change the pH level of soil, which means it can affect the acidity of the soil. 

After the mixing of cement and soil, the pH level of soil increases and makes it alkaline. 

A low pH level indicates acidic nature, and a higher one indicates alkaline nature. 

Cement should not be mixed with soil. 

It can get affected in the soil that is near areas where cement is used in construction. 

Acid rain is another major contributor in dissolving cement and its constituents into the soil, and if we use that soil for the purpose of planting, it can be very harmful to plants as well. 

Even if the sidewalks are near aggregated soil, they can destroy its ability to produce plants by affecting its acidity. 

Can Concrete Leach Chemicals into the Soil?

Yes, concrete can easily leach chemicals used in it’s manufacturing process into the soil. The most susceptible leaching of concrete into the soil is when it is freshly poured. 

Compound Formula
Calcium oxide (lime)Ca0
Silicon dioxide (silica)SiO2
Aluminum oxide (alumina)Al2O3
Iron oxideFe2O3
SulfateSO3
Chemicals found in concrete

However, other than that, it can get poured into the soil through acidic rain on pavements and buildings. 

Also, some people use pots made of concrete for holding their plants, and rain falls on those plants. The slightly acidic nature of rainwater causes the leaching of the concrete into the soil. 

After the concrete leaches into the soil then there is a higher chance that the soil becomes unable to grow healthy plants. 

The reason is concrete changes the acidity of the soil. 

Alkaline pH of Soil

 pH and Plant Growth

The only reason behind the amazing growth of plants is the nutrients available in the soil. There are different types of soil available in various regions of the world.

Some soils have more nutrients and are suitable for the growth of a specific type of plant, while others contain different compositions of minerals and acidity which may be responsible for no plant growth at all. 

The normal pH range of soil for plant growth is 5.5 to 6.5, but certain factors like the mixing of soil and cement or mixing of soil and concrete can imbalance the soil pH level, which in turn make the soil acidic, and affect the growth of plants. 

pH affects plant growth by limiting the minerals and nutrients available for the roots to absorb. Minerals are needed by the plant for healthy growth. 

Minerals and nutrients in the soil are also made available for the plants by the bacteria and microorganisms in the soil. 

The acidifying effects that cement will have on the soil can devastate the natural fauna in the soil by eradicating the beneficial microorganisms in the soil, which will, in turn, affect the healthy growth of plants. 

Managing Concrete or Cement spills on the Lawn

Oftentimes we find ourselves taking on construction projects at home. Be it to fix a broken pathway or a chipped threader on a step and the most versatile substrate is concrete. 

To get the concrete we need to mix an aggregate (gravel) with cement and water. Water causes the binding chemicals in cement to activate which fuses the gravel together to create concrete. 

During this process, mistakes happen, and oftentimes this is where cement accidentally falls on grass or areas where we have plants growing. 

When cement or concrete falls on the lawn the easiest thing to do is to just wash it down. This should not be done as it creates an unhealthy soil environment for plants to live in due to the effects on soil acidity it has. 

What you should do is take a trowel or small shovel and gently scrape off as much concrete as possible out from the spilt area. Then take a hose and wash it down using a lot of water. 

A large amount of water will dilute and spread the cement out from the area which minimizes the effects it will have on the soil, hence saving the lawn grass or other plants growing close by. 

Concrete raised bed

Is Concrete Safe for Vegetable Gardens?

Yes, but with some type of barrier to prevent chemicals from leaching into the soil. 

When you are about to grow a vegetable garden at your place, the most highlighted question is, what types of plant holders are good for growing those plants? 

You might be thinking of using concrete blocks for holding vegetable plants. 

Well, it is sometimes better to avoid concrete blocks or concrete pots for holding your vegetable gardens because the concrete can leach into the soil, making it acidic, which in turn will badly affect your plant. 

Also, there is a possibility that your vegetables will not grow in such acidic soil. Therefore, the best option is to use another type of holding structure or plant pot. 

However, if you are going to construct a raised bed garden out of concrete or cinder blocks you will want to ensure that there is some type of barrier to protect the soil from the pH swings caused by the chemicals leached from the concrete.

Will a Concrete Planter Affect Soil pH?

Yes! A concrete planter will affect the soil’s pH.

Concrete planters can leach silica and calcium oxide into the soil.

Silica is alkaline by nature and therefore will naturally raise the pH level of your soil.

Calcium oxide is alkaline by nature and will also affect plant growth. It is used as a pacifier in plastics.

The paper industry also uses it in pulping wood; because lime is highly alkaline, it dissolves the lignin that binds the fibers together.

Lignin is known for supporting the vascular tissues in plants; it’s what gives plants their hardness.

The caustic nature of these chemicals will break the lignin down and eventually kill the plants.

How to Make a Vegetable Garden Safe from the Effects of Concrete?

The best way to add protection to your vegetable garden is to line it with plastic. 

The plastic will act as a barrier from the chemicals of concrete and cement that leach into the soil with water and damage the plants. 

However, the plastic that you will use must have a thickness of around 6 mils or more because a lower thickness of plastic will be unable to protect the plants from those harmful chemicals.

In addition, for raised bed gardens built with concrete blocks, apart from plastic you can line the insides of the garden with either galvanized or metal sheeting or even plywood if you have it readily available.

The only downside of using wood for raised bed gardens, is termites. See here how to manage termites in the garden. 

Another reliable method is to seal the concrete with an acrylic or resin sealant which would lock the concrete and the harmful chemicals in place

Also, you can avoid the whole concrete issue by constructing the garden in an area where there are no concrete-made items present. 

Planting On hard surfaces

Can You Plant on Concrete?

Plants cannot be grown directly on concrete for obvious reasons. However, they can be grown in containers made out of concrete. 

Apart from concrete plant pot containers, concrete siding for raised bed gardens is a good strategy in reducing or even preventing pests such as termites which proliferate when other materials are used such as plywood or other wooden sidings. 

In these systems, the plants are planted in soil contained within the structures and the concrete just provides a sturdy structure to hold everything in place with the added benefit of pest prevention where termites are concerned. 

Concrete can be painted or even glazed with protective finishing to give your garden a more appealing appearance. 

If you have a clean concrete area and you are planning on creating a planting garden you may want to consider the previously mentioned, raised bed garden or even concrete planters. 

The Takeaway

We can conclude the topic by saying that cement and concrete can be silent killers for your plants. 

Therefore, to keep your plants safe from the harmful chemicals present in concrete and cement. You should take preventive measures to prevent spillage when working with concrete close lawns and plant gardens. 

Additionally, concrete can be beneficial in some cases where it can provide pest protection and a sturdy structure for your plants. 

JayLea

JayLea has a passion for plants and has been gardening since 2015. He has valuable knowledge about gardening and houseplant care and can answer everyday practical questions that every plant owner has.

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