How to Fill a Raised Garden Bed Without Breaking the Bank

I often hear gardeners say that when building raised beds, the beds aren’t the most expensive part of the project. It’s usually the soil that goes in them that is the most expensive part.

From creative DIY raised beds to the world’s fastest raised bed build to purchased raised bed kits, they won’t do much good without soil to fill them. But there are tips and hacks you should know to fill your garden beds on the cheap!

In this guide, I'll share how much soil plants need to grow, what to fill beds with, what not to put in raised beds, and how to fill a raised garden bed cheaply.

The Autopilot Garden

How would you like it if your garden practically grew itself with systems that save time, hassle, weeding, water, and space? Find out how to make your new raised bed garden a hands-off garden with this guide: The Autopilot Garden.

Using that and other free resources I've created, you can start a new garden with confidence! Learn how to make a garden plan, use succession planting and high intensity spacing, what to plant in February, what to plant in March, what to plant in April, and what to plant in May.

Advantages of Raised Bed Gardens

Raised bed gardens are loved by both new and experienced gardeners. They give the gardener more control over soil conditions, decreased weed pressure, better drainage, and warmer soil temperatures in the spring, all of which lead to optimized productivity.

Raised bed gardens can be easier on a person’s back and knees by eliminating the need to kneel or crouch. All these reasons make raised bed gardens popular.

How Much Soil Do Plants Need to Grow

When it comes to filling up raised beds, it’s a common misconception to think that you must fill up the entire raised bed with soil. Only filling up your raised bed halfway or three-quarters of the way with soil initially can save you around 25% of your total cost for that bed.

As long as you have at least 8 inches of soil, you can grow shallow-rooted crops (like lettuce, beets, radishes, or other leafy greens) in that raised bed. You don’t need more soil because they don’t have very deep roots.

Deeper-rooted crops (like tomatoes, carrots, and asparagus) will need more soil, approximately 12 inches deep to 17 inches deep.

Lining the Bottom of Raised Beds

Adding a liner or barrier at the bottom of raised beds usually prevents weeds from growing up into your new beds. If the soil beneath your raised bed is good quality and if you are installing the beds over basic grass or a plant-free area of soil, then you do not need to line the bottom of your raised beds.

When installing a brand new garden space at the MIgardener shop, I lined the bottom of the raised beds with a barrier. The soil there is of really good quality, but it was weed central! The barrier helps prevent weeds from growing up into the beds.

What to Fill a Raised Bed With

My preferred way to fill a raised bed cheaply is to add things that break down slowly. They will add a lot of volume to the raised bed and then, over time, break down. I add a little more soil each year as this happens.

When I am filling a raised garden bed, I add organic debris first. Fill the bottom of the bed with things like:

• Perennial Prunings - Instead of throwing these in the compost pile, use prunings to line the bottom of your raised beds.

• Yard Waste - Leaves and twigs will break down and add organic matter to your raised bed.

• Small Logs - Burying logs will decrease the amount of soil needed, help retain moisture, and create a hospitable environment for beneficial fungi.

One important thing you must know is don’t mix the organic material into the soil! Use it to fill the bottom of the raised bed and add the soil in a layer over the top. Mixing the organic debris into the soil will rob nitrogen from your soil and cause plant health problems!

Pro-Tip: Make sure there is still adequately deep soil on top of the organic debris for plants to grow in. Remember, at least 8 inches of soil for shallow-rooted plants and 17 inches of soil for deep-rooted plants, not including the organic debris!

What Not to Put in a Raised Bed

Don’t add things to your raised bed that don’t break down! They can restrict plant root growth and leach harmful things into your soil.

Here’s a quick list of items to avoid putting in raised beds:

• Tires - Tires don’t have a place in my garden. They can leach heavy metals and harmful chemicals into the soil.

• Plastic - Plastics do not fully biodegrade and they can leach BPA and microplastics into your soil.

• Styrofoam - Styrofoam is another thing that doesn’t break down. It presents several environmental and health risks.

• Rocks - Rocks can block root growth and development.

• Synthetic Materials - Synthetic materials include anything man-made with chemical processes. Instead, use natural materials in your bed that will break down, adding beneficial organic matter.

These options are not good for overall garden health, soil health, plant health, or your health!

Ways to Save Money Filling Raised Beds

We all want healthy garden soil without spending a lot. The initial investment is usually what hurts gardeners' pockets the most.

Here are tips to help you save some green to grow green.

How to Fill a Raised Garden Bed

The process to fill a raised bed is simple:

1. Add Organic Debris - Add organic material to the bottom of the raised bed.

2. Add Soil - Top that layer with a healthy layer of soil and finished compost.

3. Add Amendments - Apply an all-purpose fertilizer like Trifecta+. If you used potting mix or raised bed mix to fill the bed, amend the soil with a 2 to 4-inch layer of compost also. Spread your compost evenly across the top of the original soil, push your shovel or broad fork into the soil about 4” deep, wiggle it around, and then pull it out. Pro-Tip: If you used native soil, test the pH of your soil to see if the pH needs amending.

4. Plant - You’re ready to plant in your new garden bed!