Great Soil Is Key to a Healthy & Productive Garden

If you want your plants to be as healthy and productive (and beautiful) as possible, focus on creating a nutrient-rich soil mix for your garden. Great soil means you won't need to apply a bunch of fertilizers every 3 to 4 weeks. Your plants will mostly take care of themselves.

Soil is one aspect of starting your garden where I strongly caution against skimping. You might ultimately cost yourself way more time and money trying to improve a bad situation. Your plants will struggle and not grow to their full potential. Your garden will dry out quickly or hold way too much moisture. Poor soil is really what's at the root of so many garden issues.

So fill your vegetable garden with the very best soil possible if you want to nurture strong, healthy plants. Great soil is a mix of different elements that work together to create an amazing, rich, fertile, organic soil that’s perfect for growing fruits and vegetables. And there’s no spray bottle or synthetic ingredients necessary.

Before I give you my ideal soil mix for vegetable gardens, I'd like to teach you a little bit about the science behind your soil. That way, you can identify soil problems and amend the soil in your landscape and raised beds as needed. Let's look at the elements that make up soil.

What Is Soil Made of?

Most soil is a basic mixture of different-sized particles: sand, silt, and clay. Each of these components has a strength and a weakness when it comes to working in the garden.

Clay Gives Soil Structure

Clay has a high density of really small particles, so it's not very permeable. Clay-heavy soils offer plants plenty of nutrients and hold roots firmly in place. But too much clay in the soil means poor drainage. Clay also doesn't allow air to reach the roots of your plants. 

Silt Is Essential for Soil Fertility

Silt is considered the most fertile soil you can find for plants. Silt has intermediate-size particles and releases water to the roots of nearby plants. It provides nutrients and better water flow for your plants than clay. It's not, however, dense enough to hold together and support the root systems of your plants as they grow. 

Sand Improves Soil Drainage

Sand is basically just tiny fragments of rock, so it has much larger particles than clay and silt. The great thing about sand-heavy soil is that it drains quickly and easily (an essential for soil that's growing fruits and vegetables). That being said, sand doesn't hold together or retain much water. That means it doesn’t hold onto nutrients very well.

Organic Matter Adds Nutrients & Holds Soil Moisture

Organic matter is super important, but it makes up a small percentage of most natural soils (1 to 6%). In my garden soil blend, the organic matter of choice is compost. Compost is simply organic matter made from decomposed plant and animal materials.

Compost absorbs an enormous amount of water but drains quickly, and it holds loads of nutrients. Compost alone makes for a too-loose soil texture. It can't give vegetable roots the structure they need for stability.

What Are We Looking for in Great Garden Soil?

Let’s consider what characterizes great garden soil and look at how different soil types can have a negative effect on your garden.

Great Garden Soil Provides Structure

Plants need a good foundation for their roots as they grow. They need to feel secure, you know? That's why we don't want to grow in soils made of entirely sand or compost. We need our soil to hold together to give our plants structure.

Great Garden Soil Contains Air Pockets

We want a strong—but not a solid—structure in our ideal soil. There still has to be little air pockets throughout that the more delicate roots of annual plants can grow and expand into. This is why a soil mixture made mostly of clay isn’t ideal for herbs, leafy greens, or many fruiting plants.

Great Garden Soil Is Nutrient-Rich

Plants get many of the vitamins and minerals they need to grow from their soil. A soil that's heavy in sand wouldn't provide enough nutrients to sustain your plants over their lifetime.

So how do we get a soil blend with a strong structure, good airflow, and enough nutrients to sustain our vegetables? We create our own.

My Near-Perfect Garden Soil Mix

My custom soil blend, which I call the 103, is my variation of sandy loam soil and doesn’t include anything made in a lab. There are all kinds of recommendations for garden soil blends out there, but sandy loam is one of the most natural and easiest blends you can create. And after using this variation in hundreds of gardens, especially mine, I know it works. 

You have two options to create this ideal soil blend for your garden: Start from scratch (best for raised beds) or use soil from your landscape as a base that you'll amend for your garden (best for in-ground gardens). You can, of course, fill raised beds with amended native soil. It's much cheaper than buying soil, but you may not have enough for a large garden. You also may not be as sure about your soil elements.

What's in the 103 Soil Mix?

In my experience, the best soil for raised beds is equal parts topsoil, coarse sand, and compost, plus a little something extra. Let's look at each element.

Topsoil

You can use a locally sourced, commercially purchased topsoil, or you can simply dig up the top layer of soil in your existing landscape (your native soil). The topsoil’s main job is to hold everything else in place.

Coarse Sand

Sand’s main job is drainage. Sand particles are so large that water has a lot of routes through it. So working sand into your kitchen garden soil blend ensures the roots of your edible plants won't stand in water, which they hate. Coarse sand is what builders use for their projects—not sandbox sand. Look for "torpedo sand" at a hardware store or ask your local soil yard for coarse sand by the yard or ton.

Compost

Compost is really the magic ingredient. Find a local supplier of organic compost in your area. Landscape supply centers often carry leaf compost or, my favorite, mushroom compost in bulk.

A Little Something Extra

The "secret ingredient" in my soil recipe is a dash of animal poop. That's right. Something that’s gone through an animal’s body and come out the other side. That could be worm castings (yep, that's just worm poo), chicken manure, or rabbit poop. Since fresh manures can contain pathogens, look for fully composted or processed manures at your local garden center. Aged manures should be at least one year old.

This is how you make your garden extra productive.

How to Amend Your Existing Soil

Amending your native soil works great for in-ground gardens that will grow perennial plants. You likely won't even need to amend much if at all for wildflowers or native plants, since they're not picky about the soil and are used to growing in your area.

To amend your soil, it's a good idea to first define what already exists in your landscape or yard. Head outside, dig up a little patch of dirt, and hold it in your hands. If it's a big wet clump, it's likely made mostly of clay. If it's dry and gritty and falling out of your hands, it's mostly sand. If it's dark and crumbly, it's mostly silt or organic matter (lucky you!). Your native soil is rarely 100% any one element, but you'll likely be able to tell if there's more of one than any of the others.

Once you know what your native soil is made of, you have a better idea which soil amendments to use.

Amending Clay-Heavy Soil

To fill a raised bed with clay soil, add one shovel of sand and two shovels of compost for every one shovel of your native soil. (Don't forget the little something extra!) For an in-ground bed, dig up the top 6 inches at least of soil and mix it with one part sand and two parts compost.

Amending Sand-Heavy Soil

If you’ve got mostly sandy soil, you’ll add one shovel of compost for every shovel of sandy topsoil, plus a couple cups of castings or manure.

Amending Silt-Heavy Soil

Mix one part of your native soil with equal parts sand and compost. You may need to find some clay to dig up, too, if your soil is lacking structure.

Step One: Calculate How Much Soil You'll Need in Cubic Yards

You've got two basic routes to get this ideal soil mix into your garden: you can buy individual bags of soil, sand, and compost or you can buy soil in bulk and order a truck delivery. Bags are convenient and better for small projects, but they come with a higher price tag per cubic foot (and plastic bags, which is a bummer). A bulk order is a great way to get large amounts of soil for your project at a much lower price, but you will have a mess on your driveway and a whole bunch of soil that needs to be shoveled and transported to your garden ASAP.

Whether you buy bags or order in bulk really should come down to how much soil you need.

Raised Bed Soil Calculation

Calculate the cubic feet of each raised bed and add them together. To find cubic feet, multiply length x width x height. For my Chicago kitchen garden, the beds we built were 7ft x 2.5ft x 2ft, so 35 cubic feet each. There were 6 of them, so the total for the garden was 210.

Now convert your total into cubic yards (if you're in the US) by dividing by 27. You typically need at least 2 cubic yards of soil to merit a delivery truck from a nursery. Another option would be to bring a truck to the nursery and ask if they'll fill up the back with sand, compost, and topsoil.

If you only need 25 cubic feet or less of soil, it's best to purchase bags from your local nursery. Most bags are in 1- to 3-cubic-foot quantities, so calculate how much you'll need of each accordingly.

Step Two: Fill the Beds

Keep in mind that a yard of material weighs about 1,000 pounds. If you're filling the beds yourself, skip the gym on install day. Better yet, invite a friend to help or put your kids to work!

Here are some tips for filling your bed:

• Use a snow shovel, if you have one, to scoop soil. It allows you to get the most soil at once.
• Protect your garden bed by covering the edge with burlap or weed barrier cloth. That way, you don't have to worry about shovels or wheelbarrows dinging the sides.
• Water the soil periodically as you fill the bed to help the soil settle.
• Pause when you reach the halfway point and install your trellises. Push them all the way down, and make sure they're stabilized as you continue to add soil.
• Fill each bed all the way to the top.

You've officially completed the dirtiest part of garden installation!

Add Compost Each Season

To keep your soil healthy, add compost and natural sources of nutrients like earthworm castings regularly. One of my gardening mantras is: When in doubt, add more compost. If your plants are struggling and you suspect it's because of poor soil, adding a few inches of compost is never a bad idea. And as you fall in love with compost, as a gardener is likely to do, you can even create your own.

Get a Soil Test Every Couple of Years

Soil tests are a great way to check your soil health, specifically which nutrients are there and which are lacking. You can buy soil test kits from soil testing labs online or request one from your state’s land-grant university. There are also DIY soil test kits available, though these may not be as accurate.

If you notice your plants are not producing or not thriving (maybe they're just sitting there and not really growing), a soil test can help you address any serious issues.

That's How You Create the Best Soil for Your Plants

The 103 works very well. It’s as simple and natural of a blend as you can get while still supporting great growth in the garden. Are there other things you can add to your soil beyond these elements? Of course. But the 103 includes everything you'll ever really need. It works in raised beds and it works in containers.

The proof is in the pictures. Every garden pictured in my books and in this blog were grown with this soil blend—no synthetic fertilizers, no peat moss or vermiculite; just the 103.

All right, friends, if you've been following along with our How to Start a Garden series, then you've cleared the space and installed your garden. And now you've filled your beds with incredible soil. It's been a lot of work, but the results are worth it! The best part is, you can rest assured you've done it all the right way. You won't have to undo any of your work later. Next up, irrigation!