Gardening enthusiasts are becoming more drawn towards using raised garden beds. That’s because controlling the type of soil mix put inside those raised beds makes them ideal for planting many things. So, what’s the best soil mix for a raised garden bed?
Basically, there are a few options of soil blends that fit perfectly for a raised garden bed. That said, the most common type consists of three components: topsoil, potting soil, and compost.
In this article, you’ll learn everything about raised garden beds, how much soil they need, and the best soil mix to use. So, keep reading.
What Is a Raised Garden Bed?
The raised garden bed is a popular form of gardening where they enclose and elevate the soil above the ground inside a boxed area. Sometimes, these beds are just a few inches above the ground. Other times, they can be as high as your waist.
You can use different materials to build your garden beds, such as raw wood, treated wood, concrete, galvanized metal, or even tires. Since each material has some drawbacks, it’s a good idea to do research before deciding which one to use.
What To Include in Your Raised Garden Bed Soil Mix?
The soil is the medium you use to provide food and security to your plants. This means it creates the optimal environment for delivering essential nutrients, food, and air to the plant.
Here are a few ingredients that gardeners everywhere incorporate into their raised garden bed soil mix.
1. Topsoil
As the name suggests, topsoil is actually the upper layer of any garden or field (usually two to eight inches deep). This is where most critical processes happen because it contains nutrients and microorganisms that aid in plant growth.
You can mainly buy topsoil in bulk from a specialized supplier. As for smaller quantities, topsoil bags from any DIY store are just fine.
That said, it’s quite essential to check the condition of the topsoil you’re buying. High-quality topsoil shouldn’t contain weeds, stones, roots, bricks, or glass.
2. Compost
Compost is a mixture that gardeners use to enhance the soil’s properties. It consists of properly decomposed organic materials, such as animal products, leaves, and food scraps.
Being rich in nutrients, people add compost to their soil mixtures to nourish the plants as a natural fertilizer. Although you can find compost at your local garden center, it’s not hard to make your own compost heap.
3. Vermiculite
Basically, vermiculite is a processed mineral that provides excellent soil aeration and drainage, just like perlite. It also enriches the soil with many nourishing substances.
Unlike perlite, vermiculite can absorb and retain nutrients and water. That’s why it’s definitely a better substitute. Some of the vermiculite’s qualities include being:
- Sterile
- Non-toxic
- Odorless
- Mold resistant
- Immune to rot or deterioration
- Lightweight
- Easy to mix with the soil
- pH neutral
4. Organic Matter
Another beneficial component to add to your raised garden bed soil mix is organic matter. Mediums like grass clippings, composted wood, worm castings, composted poultry or cow manure, and leaf mold can all improve the soil’s structure and quality.
5. Other Materials
Aside from vermiculite or perlite, experts recommend adding other materials to enhance drainage. That’s especially if the garden bed sits directly on solid ground like concrete. So, you might want to cast a layer of stones or debris at the base of your garden bed.
What Is the Best Soil Mix for a Raised Garden Bed?
It’s quite essential to know that there’s no such thing as a perfect soil mix for raised garden beds. Instead, there are a few excellent components to add together and make what best fits your needs.
The components and quantities of soil mixes depend on what you want to plant and the local climate of the region you’re living in.
Primarily, there are many blends gardeners use for their raised garden beds, take a look at a few of them:
- 50:50 Soil Mix: This is one of the most common soil mixes consisting of 50% topsoil and 50% compost. These ratios ensure healthy plant growth with proper nutrition.
- 70:30 Soil Mix: Adding 50% compost to the blend can be a bit costly. That’s why some gardeners tend to change that ratio to 70% topsoil and 30% compost. It actually works fine for a ratio up to 95:5.
- 60:30:10 Soil Mix: So, now you know that topsoil and compost are essential for most mixtures. However, what you add to them can vary from one blend to the other. In this mix, you can add 10% potting soil containing peat moss and vermiculite.
Soil Mixture for a Vegetable Garden
As previously mentioned, the components of a soil blend depend on many factors. One of the most critical factors is what you’re planning to plant. That said, the soil blend for a vegetable garden should contain lots of compost and organic matter.
One of the best soil mixes is a combination of three materials in equal amounts. These materials are topsoil and compost, with the addition of coconut coir or peat moss.
Conveniently, you can find ready-to-use mixes in the market. These blends already have topsoil, organic matter, peat moss, fertilizers, and compost. What’s more, you can find what plants they work best for listed on the package.
Moreover, you can buy specialized soil mixes for different kinds of crops. That’s because different plants need various amounts of certain nutrients.
Vegetables like onions and carrots, for example, naturally need more potassium than other plants. That’s why it’s essential to have an idea about the needs of your crops before putting together their soil mixtures.
Soil Mixture for a Flower Garden
Most flowers thrive in fertile soil that’s well-drained yet still moist. So, for growing your own flower bed garden, you need to have loam or sandy loam soil. Furthermore, combining compost and peat moss into the soil improves its ability to retain moisture and circulate air.
So, if you have large raised beds, use a mixture of equal parts soil and organic matter. As for smaller flower beds, a blend of two parts of both soil and organic matter with one part inorganic matter works just fine.
Another option is to opt for soilless mixtures that contain mostly compost. These mixes are naturally sterile, as the composting process can destroy most pests and harmful weeds. Additionally, they’re lightweight, making them perfect for large flower beds.
To create a soilless mixture, mix two equal parts of compost with perlite or peat moss with vermiculite.
Having said that, it’s essential to consider adding some nutrients for the flowers to grow healthy. Although these nutrients depend on the type of flowers you’re planting, starting with a general-purpose fertilizer is just fine.
What Are Essential Soil Nutrients To Include in a Raised Bed?
Aside from the hydrogen, oxygen, and carbon obtained from the atmosphere, there are 15 essential elements the plant needs. Oftentimes, gardeners can manage and control the presence of 12 “mineral nutrients” in the soil.
Those 12 nutrients are mainly divided into three groups, which are:
1. Primary Nutrients
Although they’re just as crucial as other elements, plants require primary nutrients in large quantities. You may be familiar with those elements, as you see the symbol “N-P-K” printed on commercial fertilizer bags.
Those letters refer to Nitrogen (N), phosphorus (P), and potassium (K).
2. Intermediate Nutrients
Intermediate nutrients are simply magnesium, sulfur, and calcium. When combined with primary nutrients, together they’re commonly known as macronutrients. Usually, plants need intermediate nutrients in much smaller amounts than the primary ones.
3. Micronutrients
The six remaining elements are the micronutrients, and they’re just as essential as the others. The only difference is that the plants require them in such small quantities that they’re actually expressed in parts per million. Here’s a list of micronutrients:
- Iron
- Zinc
- Boron
- Copper
- Manganese
- Molybdenum
How To Make Your Own Soil Mix for a Raised Bed (3–5 Steps)?
Although there are many available premixed soil mixtures for raised bed gardens, it can be pricey to buy them.
Not only does making your soil mixture save money, but it also gives you a great sense of achievement. Plus, with time and expertise, you’ll be able to determine what works best for your garden.
Step #1: Get the Ingredients
For a DIY soil mix, you need three products: topsoil with compost (or just compost), peat moss, and vermiculite.
Topsoil and compost both come in prepackaged form. However, if you have the time and space, making your own compost saves you money.
As for peat moss and vermiculite, you can find them in the nearest DIY store. They’re quite useful because, as previously mentioned, they improve aeration and water retention.
Step #2: Line the Garden Bed
Before adding the soil components, you should line the empty garden beds, preferably with cardboard or newspapers. That’s because this layer can prevent deep weeds from spreading through the garden bed.
Then, you need to fill the bottom of your garden beds with whatever organic matter you can find in your yard. Things like dried leaves, branches, or logs can fill up the bottom third of the garden bed effectively. This way, you save the top two-thirds for your (more expensive) soil mix.
Step #3: Add and Mix
Now that you have all ingredients prepared and garden beds ready, it’s time to work on the mixture. You need to add equal amounts of compost, peat moss, and vermiculite.
Start by layering each component interchangeably, creating thin tiers. When the garden bed is halfway full, use a shovel or hoe to mix the ingredients. Then, continue layering the rest of the components, and repeat until completely full.
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How Much Soil Do You Need?
It’s vital to know exactly how much soil you need, not to buy too much or too little. The soil bags you find at the store are essentially sold in cubic yards. So, to know how much soil you need for your raised garden beds, you need to measure them.
Basically, when you multiply the length, width, and height of each bed in feet, you get the volume in cubic feet. Add the total volume of all garden beds to get the total cubic feet of soil needed. Finally, by dividing the total number by 27, you calculate the volume in cubic yards.
How To Amend the Soil in Your Garden Bed?
With time, plants use up most of the nutrients in the soil. That’s why you need to amend your garden bed soil regularly. By doing so once or twice a year, you’ll notice amazing improvements in the quality and richness of your soil.
For best results, amend your soil after gathering all crops and before you plant the next round of your seasonal plants. Adding a layer of compost (one to two inches thick) should do the trick.
Using Compost for Raised Beds
Compost is a great and vital addition to any kind of soil. Whether you get it from your own compost heap or the store, you can’t have a perfect soil mixture without it.
Using compost for raised beds has many benefits, including:
- Improving the soil structure
- Helping the soil retain moisture and nutrients
- Acting as a natural fertilizer, containing microorganisms like fungi and bacteria
- Containing essential nutrients like copper, nitrogen, phosphorus, and zinc
- Making the soil healthy and plant more pest resistant
What Are the Benefits of a Raised Garden Bed?
Since gardeners everywhere are now using this planting style more than ever, it has to have some advantages to it. So, what makes raised-bed gardening so popular?
Take a look at some of the benefits related to using raised beds for planting different crops:
1. Keeping the Soil Fluffy
When you use raised garden beds, you get to keep them away from foot traffic. That’s especially when you have kids helping you. This, in turn, ensures that the soil stays fluffy and loose.
2. Less Maintenance
As previously mentioned, the soil of raised garden beds doesn’t suffer from compaction. Consequently, it doesn’t require regular maintenance operations, like tilling.
Additionally, as long as you properly care for the soil, the weed population decreases. So, weeding also becomes less of an issue.
3. Longer Growing Season
With the right soil mix, raised garden beds tend to warm up more quickly than the ground’s soil. That’s especially around springtime. Therefore, raised-bed gardening allows for better planting conditions and a longer growing season.
4. Defying Surrounding Conditions
Perhaps the greatest benefit of raised-bed gardening is the ability to grow plants everywhere. Areas that don’t even support gardening, like parking lots, can become a haven for plants. What’s more, raised garden beds can act as terracing on steep slopes and uneven surfaces.
5. Other Benefits
- Easier manageability
- Better drainage
- Flexible soil amendments
- Less material waste
- More suitable access for people with disabilities
- Well defined boundaries
- Fewer pests
FAQ
Q1: When to replace soil in a raised garden bed?
Technically, you never need to replace the soil in a raised garden bed. Instead, you should only amend the existing soil to restore nutrients and enhance plant growth.
Q2: What layers of soil go into a raised garden bed?
After lining your raised garden bed with newspaper or cardboard, the next step is to add your soil mix. Here is one of the examples of layering the soil from bottom to top:
- Organic matter (twigs, bark, branches)
- Less expensive soil or loam for filling, only if your garden beds are too deep
- High-quality soil mix
Q3: How do I layer the bottom of a raised garden bed?
You just need to line the bottom of your raised garden beds with newspapers or cardboard. For extra weed protection, you can use geotextile or weed matting to help repress the growth of harmful weeds through your garden beds.
Q4: How deep should I keep the bed soil?
To ensure optimal root growth, your raised garden beds should contain at least eight inches of soil. So, to be safe and to ensure your garden beds are suitable for most gardening situations, you need to fill them with 12 inches of soil.
Q5: What if the raised garden bed is too dry?
If you notice that the surface of your garden bed is too dry, grab a hoe and run it through the top couple of inches of the soil. This way you break up the soil and make it easier to treat.
Then, apply at least three inches of fresh compost and water thoroughly. Not only does compost help retain moisture and protect the soil from drying out, but it also adds extra nutrients to it.
The Bottom Line
It’s amazing to grow your own food and have a beautiful raised-bed garden. However, to enjoy maximum yield, you need to learn how to make the perfect soil mix for a raised garden bed.
Although the 50:50 mix is the most popular, there’s no perfect blend that works with everything. Rather, adding together some of the essential ingredients to fit your plants’ needs is what makes a great mix.
Lastly, as long as you use high-quality, organic products, you’ll have the garden of your dreams.