Compost, Topsoil, Potting Soil: Which Should I Buy For My Raised Beds?

Raised beds are a unique way to grow vegetables or flowers and have recently become more popular as many people have less space in their yards. However, it is important to choose the right kind of soil to ensure healthy plants.

Compost, Topsoil, Potting Soil: Which Should I Buy For My Raised Beds?

An ideal soil mix for raised beds combines topsoil, compost, and some of the components of a potting soil like perlite, vermiculite, and coconut coir. This will essentially create the best and most affordable “raised garden bed potting mix” for you to plant into.

In this article, we’ll review the different types of soils, the benefits of each, and how to create the right mix for your raised beds.

Why Is The Right Soil Important For Your Raised Beds?

The three main components of successful gardening are sunlight, water, and soil. There isn’t a lot you can do about sunlight other than trying to position your raised beds in an area of your yard that isn’t shady. Watering you have some control over but the rain is out of your hands! 

Soil is the one thing that you can have complete control over when it comes to gardening in raised beds. This combination of sun, water, and soil help to ensure that your garden is as successful as possible and produces beautiful, healthy plants.

Choosing the right soil is important because it is the environment in which your plants live. Having healthy soil creates an ecosystem in which your plants will thrive and means your flowers and vegetables will be healthy. Without proper soil, your plants will not obtain the nutrients they need to grow.

Good soil allows air to flow through it and around the roots of your plants. If there isn’t adequate airflow in the soil, water won’t drain properly. Soil that is too wet can lead to fungus growing in the soil. If your plants become infected, it can be very challenging to get rid of and you may need to replace everything.

What is Compost?

Compost is the material that is created when organic matter decays. This organic matter can include things such as fruit and vegetable scraps, grass clippings, egg shells, coffee grounds, leaves, and animal manure. When these items decompose, they create a rich organic substance that is full of nutrients.

You can purchase compost at garden centers or you can make your own. There is a wide variety of store-bought options that range in quality and price. Using compost that you have made ensures you are aware of the ingredients. An added bonus is that making your own compost is free!

Another option for obtaining compost is to check with your neighbors. They may produce more compost than they are able to use in their gardens and might be happy to give you some at no cost.

Compost is used in gardens to add nutrients and moisture to the soil which feeds the plants. It improves the drainage of the soil and helps improve airflow around the roots. Using compost can also help minimize the number of weeds in your garden.

What is Topsoil?

Topsoil is a soil type often used as a filler in gardens. It is not particularly rich in nutrients although it does contain organic matter and is an important part of your raised bed soil mixture. There is a difference between naturally occurring topsoil and the bagged topsoil you find in the store.

Natural topsoil is essentially the top layer of the earth’s surface. Since there is a vast range of environments, the quality of the topsoil varies from place to place. Depending on where you live, the topsoil may be predominantly sand or clay which is not ideal for growing.

Topsoil that you purchase at a garden center often has stones and other debris removed from it before packaging. Commercial topsoil sometimes contains soil that has been sourced from multiple areas. Purchasing topsoil can be a good idea if your yard’s natural topsoil is not suitable for planting.

You can also purchase topsoil in bulk from a landscaping company. This can be a cost-effective way of getting the material since the company passes along the savings that they get by buying it in large quantities. 

What is Potting Soil?

Potting soil is a type of material that is specifically designed for growing plants in containers. It is often used for indoor houseplants as well as outdoor plants in pots or raised beds. 

The components of potting soil vary from one manufacturer to the next, however, the ingredients should be listed on the packaging for you to review.

Potting soil often contains peat moss which helps the soil retain moisture. Your potting soil may also include compost, perlite, manure, grit, sand, coconut coir, vermiculite, or grit. Some potting soils contain added fertilizer.

While you can purchase an all-purpose type of potting soil, there are also potting soils created specifically for raised beds, vegetables, flowers, or succulents. Regardless of what you are planting, you should be able to find a potting soil that is suitable for you.

What Type of Soil is Best?

When getting started with your raised beds, choosing the soil is the very foundation of a successful planting season. We recommend using a mixture of topsoil, compost, coconut coir and vermiculite in a 40-30-15-15 ratio. This mixture and ratio is one that works well for me but opinions vary and I think other mixtures can work just fine as well.

How Much Do You Need?

If your raised bed is 8’x4′ and 12″ deep it will require a total of 32 cubic feet of soil, you would use 12.8 cubic feet of topsoil, 9.6 cubic feet of compost, 4.8 cubic feet of coconut coir, and 4.8 cubic feet of vermiculite. This helps to ensure that your raised bed has proper airflow, adequate moisture retention, good drainage, and enough nutrients.

Use the calculator below to determine how much of each component you will need to fill your raised garden beds.

While some gardeners suggest arranging your soil in layers, it is best when setting up your raised beds to mix all of the components together. I like to pour all the components onto a large tarp and pull the tarp from the sides back and forth to mix everything together then shovel it into the raised bed.

Keep in mind that your requirements may differ based on the environment in which you live and what types of plants you have. You might need to alter the ratio slightly until you find a combination that works best for you. Many gardeners find that it takes a couple of growing seasons before they find what really works for them.

Tip: If Your Raised Beds Are Deeper Than 12 Inches You Can Add Small Logs And Branches To The Bottom Of The Beds As Filler. This Biomass Debris Will Break Down Over Time, Help Retain Moisture In The Bottom Of The Bed And Save You Some Money.

Buying Soil After the First Year

Now that you know what type of soil to buy to set up your raised beds, you’ll be well set up to maintain them going forward. In terms of expenses, your biggest output will be that first season when you need to fill the entire bed.

The great thing about gardening soil is that it improves over time. You will find that the quality of soil in your raised beds gets better each growing season. However, since every plant you grow takes nutrients from the soil, you need to replenish the soil every year.

The best way to keep your soil full of nutrients is to add compost. You can do this either at the beginning or the end of the growing season–it’s up to you. Each year, add a top layer of compost to all of your raised beds. You don’t need much–about a half inch to evenly cover the top will be enough. It’s not necessary to mix it in with the existing soil, just leave it to sit on top.

adding compost

Replenishing your soil in this way will add a healthy dose of nutrients to the soil. This ensures that each crop of vegetables or season of flowers will grow to its fullest potential. And over time your beds end up with a richer, healthier soil due to the organic matter you add every season.

Final Thoughts on Soil for Raised Beds

Using raised beds can be a great way to grow your vegetables or flowers. Choosing the proper combination of soil types will go a long way to producing healthy plants. Be sure to check the packaging for a list of the ingredients as not all brands are the same. 

While it can be tempting to cut costs on soil, remember that the quality of soil you use will influence the quality of the plants you grow. Making an initial investment in your first growing season will reward you each year that follows. With the right soil, your garden will produce plenty of flowers and vegetables for you to enjoy every season!

Frequently Asked Questions

How Many Cubic Feet Are In A Cubic Yard?

There are 27 cubic feet in a cubic yard.

How Many Cubic Feet Of Top Soil Is In A 40-Pound Bag?

There is approximately .75 cubic feet of topsoil in a 40-pound bag.

How Many Cubic Feet Of Compost Is In A 40-Pound Bag?

There are approximately .75 cubic feet of compost in a 40-pound bag.

How Many Cubic Feet Of Vermiculite Are In A 20-Pound Bag?

There are approximately 4 cubic feet of vermiculite in a 20-pound bag.

How Many Cubic Feet Does A Brick Of Coco Coir Make?

A 10-pound brick of coconut coir makes approximately 2.25 cubic feet.


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    Author, blogger, podcaster, homesteading and permaculture enthusiast. I have a passion for sharing what I learn and helping others on their journey. If you're looking for me, you'll usually find me in the garden.

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    Harold Thornbro

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