Square-Foot Gardening Soil Mix [Best Tips & Tricks]

Everyone is making their own gardens. Perhaps you’re thinking about getting your hands dirty too.

Backyard gardening isn’t just a trend. It’s about harvesting quality produce that is sustainable and healthy.

But is your garden space big enough? Those digging in the soil say it’s rewarding even on a small scale.

Perhaps you’re overwhelmed by getting the square-foot gardening soil mix just right. Before investing your time and resources into a garden project, here’s what you should consider.

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Accessing Your Garden Space

Is digging up that high water-consuming patch of lawn worth the effort? Is it possible to start a garden on your balcony? Yes—even in challenging Hardiness Zones, you can harvest plenty.

The vital component of gardening is understanding your climate zone, which defines your hardiness zones. But don’t despair if you live in the northern parts of the US.

Some vegetables like lettuce, radish, rutabaga, and many others prefer cooler growing conditions. Building a raised garden bed is fun and enjoyable for the entire family.

Hardiness zone states (3-4) like Montana, North Dakota, Vermont, Minnesota, Michigan, New York, and Maine have many successful garden plots.

Creating the perfect square-foot gardening soil mix is crucial.

What Defines Square-Foot Gardening?

  • Creating the perfect planting soil
  • Growing plants in raised beds/containers
  • Consider using soilless mixtures
  • Using smaller spaces
  • Designating the optimum area in a garden
  • Maximizing your growing space
  • Creating the right balance of soil and plants

Check out: Okra square foot gardening

The Basics of Square-Foot Gardening Soil Mix

Active gardening takes just as much planning as it takes physical effort. Don’t let all the information overwhelm your desire to start a garden.

Once you understand the basics, you’ll see how easy it is.

For individuals who don’t want the mess of soil, or have limited space, consider soilless gardening mixes. Soilless is ideal for vertical gardens, balconies, or rooftop container gardens.

An essential element of soilless gardening requires researching what types of vegetables you want. If you’re thinking of soilless gardening, you might want to redirect here to the specifics.

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Staking Out Your Growing Area & Building a Raised Garden Bed

Measuring the growing area takes a bit of math. Volume is a measurement equal to your container space’s width, length, and height.

This equal ratio applies regardless of whether you live in Montana, Mississippi, or Missouri.

Volume = length x width x height (of your container bed)

This example uses a rectangular standard-sized raised garden box with an average-sized wooden frame.

The length is 6 feet, the width is 3 feet, and the height is 16.5 inches (or 1.4 feet).

6 x 3 x 1.4 = 25.2 cubic feet

Divide that answer by 27 to get cubic yards.

The required soil amount is 0.9 cubic yards of soil.

L-Shaped or U-Shaped Garden Bed

Use these calculation methods if your raised garden bed is a more complicated structure, like an L-shape or U-shape.

L-shape configurations:

Volume = L x W x H + L x W x H

Here are some random sample numbers: 6 x 3 x 1.4 + 3 x 3 x 1.4.

Volume = 25.2 + 12.6 = 37.8 : 27 = 1.4 cubic yards

For cubic yards, divide the total volume by 27. The total is 1.4 cubic yards.

Repeat measurement for U-shaped raised garden boxes, but omit the inside dimensions of L-shaped boxes.

Round, Oblong, or Cylindrical Containers

The calculation principles remain the same as rectangular or square-shaped gardening soil mix volumes.

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Ingredient List for Square-Foot Gardening Soil Mix

Typically, garden centers or building supply stores sell gardening soil mix ingredients in cubic feet measurements. Here is a simple calculator to convert those to numbers.

For the best garden soil mix blend, gardeners look for soil that isn’t too sandy or too loam dense.

Sandy soil doesn’t hold moisture. Loam-dense soil is difficult to work with and holds onto water. A perfect blend uses organic materials that create the ideal components for seedlings to thrive.

  • Peat moss
  • Vermiculite
  • Compost

These key ingredients are ideal for square-foot gardening raised flower beds. This blend provides plants with the basic materials for perfect growing conditions.

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Peat Moss

Peat moss is harvested from remote areas in Canada. It’s another naturally occurring ingredient in making an ideal gardening soil mixture.

On its own, peat moss is not a perfect component. It’s an ideal partner blended in equal portions with vermiculite and compost. Peat moss is on the acid scale of the PH balance.

Peat moss is free of weeds and holds its weight in moisture, which it releases to seedlings and plants without drowning the delicate root systems.


Magnesium aluminum iron silicate, commonly called vermiculite, is a mined mineral that occurs in the USA. It’s a lightweight component and doesn’t disintegrate over time with a neutral PH.

Vermiculite is the most expensive part of the square-foot gardening equation. However, once it’s in place, it’s there for the duration and won’t break down.

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Many avid gardeners build their own natural organic fertilizer from kitchen waste (not including meat or fats). Compost provides your plants with the necessary nutrients in a slow-release method, unlike chemical fertilizers.

Compost is beneficial in numerous ways:

  • Improves soil texture
  • Provides beneficial organisms like fungi and bacteria
  • Adds nitrogen and sulfur (both are essential to plant growth)
  • Helps to retain moisture
  • Keeps waste out of landfills

The perfect blend for creating a square-foot gardening soil mix is equal parts of peat moss, vermiculite, and compost. This texture will be lightweight and has water-holding properties.

This blend is ideal for gardens in all parts of the USA, from Montana to California. It’s suitable for all hardiness zones.

Tip: If you’re standing at the garden center wondering what the difference is between perlite and vermiculite, you’re not alone.

Both are naturally occurring minerals and soil amendments but with different usages.

Neither vermiculite nor perlite decomposes.

Perlite has the advantage of helping loosen hard-packed soil. It also provides superior soil drainage. Vermiculite is best for preventing moisture loss. They have a PH balance of 7.0 to 7.5.


Gardening doesn’t have to be an expense. Many materials are free or low-cost if you shop around.

Peat Moss

Buying sphagnum peat moss in a compressed format is the most cost-effective.

The downside to buying it in (approximate) 2.2 cubic foot bales is getting it home. On average, a bulk bale is around $8 to $10.


Vermiculite is the most expensive ingredient in your mixture. While prices may vary, expect to spend $57/1 cubic foot of horticultural vermiculite.


Compost can be free if you want to create your own organic mixture. You can have your own compost in a few weeks, but it requires some planning and heavy lifting.

For example, one cubic foot of steer manure costs as little as $3.00 at your local building store.

There are many types of compost, from steer, sheep, and horse manure to fish and bone meal.

The longer you garden, the better you’ll become at estimating which compost blend produces the best results.

Some municipalities have composting programs and will deliver large sacks of compost to your door.

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Creating the Perfect Square-Foot Gardening Soil Mix

Raised gardening boxes are a superior way to garden for many reasons. One of the upsides is getting your vegetables or flowers off the ground for easier access.

There are several ways to mix the equal part components without breaking your back.

  • Mix off the ground in a wheelbarrow (in smaller portions)
  • On the back of a truck bed
  • On the ground on a tarp

A standard wheelbarrow is like a measuring cup and holds 3 cubic feet of volume. Shallow wheelbarrows hold about 2 cubic feet.

For larger projects, mixing the ingredients on the trap is the easiest method. Remember that you’ll be using the ingredients in three equal measures by volume.

Blend the materials using smaller shovels as you go instead of dumping all the materials. It saves your back and ensures that the mixture blends well.

Once you blend the ingredients well, the soil mixture you’re creating is lightweight, uniform in color, and has a loose texture.

A well-blended mix provides your plants with the optimal starting point. If your mixture is not blended correctly, you might have clumps that prevent proper drainage.

Shovel the perfect mix into your garden container or raised garden bed.

Perfecting the Garden Soil Mix Inside Your Raised Bed

After you transfer all the soil materials into your container, smooth it out with a rake and lightly tamp it. Gardeners know that seeds and seedlings require loose yet firm soil to grab.

If your soil is too loosely packed, the water will drain too quickly or pool if packed too tightly.

Seeding and seedlings from seed need something firm to cling to. A perfect blend provides the necessary growing components.

You probably have a menu of vegetables for fruits you want to plant. Companion planting is an important consideration and not an old myth. Ongoing studies prove its impact.

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Additional Soil Helpers

Some garden beds thrive with a few additional soil boosters. Some people have a green thumb and grow just about anything. Others struggle to produce anything but weeds.


The sun provides one of the key ingredients to successful gardening—light. Too much light can be fatal, as is not enough. Consider sun exposure when locating your raised garden.

Healthy plants require a minimum of six hours of sunlight; eight hours is even better. However, some areas become natural suntraps based on a home and garden’s configuration.

Too much sunlight will scorch your plants. A good way is to observe the sun’s cycle. Find the best location that falls somewhere in the middle between light and shade.

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A raised garden bed will need regular watering. Moisture is one of the three prime elements of gardening. An easy reach of a water source to a raised flowerbed is best.

Your plants will suffer if your raised garden is too far from a water source. It’s common for inexperienced gardeners to think that dragging a hose to the raised bed isn’t a problem. It is.

Eventually, dragging that hose will become a nuisance, and you’ll neglect to water. Rainfall is nature’s best watering can. Some plants, like tomatoes, may develop diseases from too much.


Plants need nutrients to thrive. Vital nutrients can come from natural or chemical fertilizers. Fertilizers are organic or inorganic. The organic variety comes from manure, bone meal, compost, or other natural components.

Inorganic fertilizers contain a controlled nutrient content, meaning each bag has the same precise formulation.

A good base formula for inorganic fertilizer for vegetables is 10-10-10 or 5-5-5. Of course, there are dozens of alternatives and brand varieties.

Acidic or Alkaline PH Balance

The acidity or alkalinity of your gardening soil mix significantly affects results. Most vegetables prefer a neutral PH balance. Farmer’s Almanac is an excellent resource for vegetable PH.

Raised Beds and Container Gardening Types

People are inventive. There are many ways to create a raised garden, but amend your square-foot gardening soil mix according to the type.

Raised flower beds are easier to manage for adults and children. It also helps to avoid some garden pests.

Types of Raised & Container Beds

These are the different kinds of raised and container beds:

  • Traditional wood frame ground level
  • Elevated wood frame boxes on stands
  • Tiered wood-farmed boxes
  • Galvanized bins
  • Plastic prefab containers
  • Movable on wheels
  • Vertical containers (as in tubes)

Many more people have success using regular garden pots, inside building blocks, tires, logs, bathtubs, jars, and troughs.

As long as you apply the square-foot gardening soil mix equation, you’ll see results.

Square Foot Gardening Soil Mix
Square Foot Gardening Soil Mix

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Calculating the square-foot gardening soil mix isn’t as complicated as it first sounds. Remember to use equal parts vermiculite, peat moss, and compost.

Once you blend the ingredients and gently plant your seeds or seedlings, you’re a gardener.

Adding sunlight, moisture, and additional nutritional compounds is all that’s needed. Sit back, watch it grow, and enjoy.