Are Concrete Blocks Safe for Gardens?

When it comes to growing food in a garden, you want to ensure that everything is suitable for human consumption. This includes the materials in the garden, the content of the soil, and the plants. So, are concrete blocks safe for gardens?

Concrete blocks are safe for gardens. Concrete blocks don’t have the potentially contaminating ingredients found in some old cinder blocks. However, even modern cinder blocks are largely safe to use in gardens as they lack harmful particles.

If you have been considering using concrete blocks in your garden, this article will explain everything you need to know. I’ll discuss how to use them, and when to avoid them. Let’s get started! 

Concrete Blocks Explained

Concrete blocks aren’t known for their esthetic qualities but have many practical applications. They are becoming increasingly common in greenspaces across the country.

Concrete blocks are made from a combination of several ingredients, including:

  • Stone
  • Sand
  • Wood
  • Steel
  • Cement

They are large and can withstand high amounts of pressure, and, because of their strength, are often used in construction projects. Concrete blocks are also cheap to purchase, easy to produce, and can be used for a wide range of applications. 

However, this hasn’t always been the case, with many people still referring to them by their old name – cinder blocks. Unlike concrete blocks, cinder blocks are much less strong, can’t withstand as much pressure, and are made from ash, concrete, and cinder.

Although their differences aren’t apparent to the naked eye, how cinder and concrete blocks differ is very important. The main difference is also what, in part, makes concrete blocks better to use in gardens.

Why Concrete Blocks Aren’t Popular in Gardening

While it might seem like concrete blocks are a great material to use in different gardening projects, many people have been told to avoid using them for many years. Nonetheless, they have been used in other outdoor projects, and in many building projects. 

Ultimately, the reasons against using concrete blocks for gardening are unfounded or antiquated. Since many people still call concrete blocks by their old name (cinder blocks), some are still afraid to use them in gardens, simply because they don’t realize the difference between concrete and cinder.

Unlike their modern counterparts, traditional cinder blocks are made from fly ash, a material that is a byproduct of burning coal. Fly ash can break down easily, and the leftover ash can seep into the soil, and then into the ground. If this occurs, these materials could then be absorbed into the food we eat, making it so we consume toxic waste that can lead to lung issues, cancer, and other diseases.

Modern cinder blocks don’t typically use fly ash. Unless you are using a very old block, you don’t need to worry about fly ash, making the arguments against using them invalid.

How To Use Concrete Blocks In Gardening

The most common use for concrete blocks in gardening is for stand-up flower beds, but you can use them for other purposes. Let’s look at a few common uses of concrete blocks in gardening:

Raised Flower Beds

Raised flower beds are a great way to ensure that plants can get the correct amount of nutrients without worrying about overwatering. Raised flower beds create more aerated soil, drainage, and fewer weeds. 

Using old concrete blocks to make these beds is a great option. Pile the blocks a foot high in a rectangular shape. Fill the box with soil, and you have a raised flower bed.

Vertical Gardening

In densely populated areas, growing plants can be a real challenge due to a lack of space. Vertical gardening is a new phenomenon that makes up for this trend. 

You can stack concrete blocks on top of one another and cover one side of the holes they often contain. Fill the holes with soil and a small plant and you’ve made your own pot. Stacking the blocks on top of one another allows you to grow plants vertically. 

Garden Fencing

Many plants that grow on vines require some sort of structure for them to wrap around. Using cement blocks to help garden fencing is a great way to encourage vine life and make your garden more aesthetically pleasing. 

Stand your concrete blocks upright and run a wooden beam through them. Plant vines at the bottom of the fence, and watch as it transforms into a beautiful vine-covered fence.

How to Use Broken Concrete Blocks For Gardening

If you have old, broken concrete blocks, it can feel like a shame for them to go to waste. Luckily, there are various interesting ways to incorporate them into your gardening. 

Let’s take a look at a few examples: 

Use Broken Concrete Blocks With a Lining

If you’re worried about the chemicals in your broken concrete blocks leaching into your soil, you can use them with a lining or a barrier. 

When the exposed interior of the block interacts with the weather, it erodes, and a plastic lining can prevent soil leaching.

You can also use a sealent to prevent the blocks from eroding faster. A polymer paint, for instance, is a great way to do this.

Use Broken Concrete Blocks On Stone To Prevent Leaching

Another fantastic way to use broken concerte blocks without worrying about chemical leaching is to use concrete blocks on stone. If the concrete blocks are placed on stone, the chemicals wouldn’t be absorbed into the soil.

When using concrete blocks on stone, you would only need to treat the soil inside the broken concrete blocks. 

Use Broken Blocks In Garden Areas To Prevent Vegetation Growth

If you have areas in your garden where you want to prevent weed and other vegetation growth, broken concrete blocks work well. 

You could grind up the concrete blocks and spread them around invasive plants to prevent spread. Alternatively, simply place small chunks of concrete in weed-prone areas. 

Use Broken Concrete Blocks for Paving

Do you have an upcoming paving project? If so, consider using some of the broken concrete blocks for your paving project. If you have many broken pieces, you could make a unique-looking garden path. 

Before using the broken concrete blocks for paving, spread a layer of sand on the soil to promote water drainage. 

Use Broken Concrete Blocks for Planters

Another fantastic use for broken concrete pieces is for making planters. You could fashion a few pieces together to form a bowl or pot-like shape, and then line it with plastic before filling it with soil. 

Alternatively, consider using some pouring concrete to stick the pieces together and create your desired shape. 

When To Avoid Concrete Blocks in a Garden

While concrete blocks are safe for use in a garden and provide many helpful qualities, there are times when using them is not helpful. For example, if you need your plants to be able to drain easily, surrounding them with concrete blocks decreases drainage. 

As long as there is drainage on the bottom (such as a raised flower bed) this is fine, but plants inside concrete blocks may have a hard time.

Another instance to avoid concrete blocks is when you have plants that are very heat sensitive. Concrete can absorb heat easily, and retain it for a long time. However, the energy needed to warm these blocks is incredibly high. If you need your plants to be able to adapt to the temperature, using concrete blocks can be challenging.

Finally, using concrete blocks for gardening is not always visually pleasing. You can make the blocks look nice, but it often takes extra work. If you want a beautiful garden and not necessarily the most practical one, the blocks might not be your best friend.

Final Thoughts

Despite the misconceptions surrounding concrete blocks, they are incredibly different from cinder blocks and are absolutely safe for gardening. Concrete blocks have many practical uses, and can be used in a wide variety of ways. For more ideas on how to use concrete blocks in gardening, consider looking at Pinterest.

However, know that concrete blocks aren’t always the best for gardening. They can reduce drainage, deregulate temperature, and are not always visually pleasing. Consider these factors when deciding if to use concrete blocks for gardening.

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

Recent Posts