How to Fill a Raised Bed for Cheap (Without Ruining Your Soil)

Like many optimistic gardeners who’ve come before you, maybe you budgeted for the plants and the materials to build a raised bed but forgot about the soil you’ll need to fill it. It’s only once you’re standing in the hardware store calculating the total of all those soil bags that you realize: 

Dirt may be cheap, but soil is a whole different story. 

I’ve got good news for you: To save money on your initial raised bed setup, you do not need to fill your entire raised beds with store-bought soil. Instead, you’ll use one of these five budget-friendly (if not free) methods to fill the bottom portion of your bed with organic materials that will become soil in the future. This is an effective and relatively easy way to cut costs. 

You don’t need to take out a second mortgage to fill multiple raised beds. But you will need some patience. It also helps if you have a lot of organic materials lying around. (And between your kitchen and your yard, you probably have more than you think!) 

Keep reading to learn the best ways to fill a raised garden bed in your home garden without breaking the bank. 

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WHAT YOU PUT IN THE SOIL MATTERS

If you want to have a successful raised-bed garden, you have to think of what you fill your raised beds with as so much more than just filler. 

Good soil is a living system teeming with worms, fungi, and microscopic organisms. These little guys are important because they break down organic matter, make nutrients readily available, and help suppress disease that could spread to your plants. 

The more life you have in the soil, the more life (think: your plants) it can support without needing tons of artificial inputs like Miracle-Gro.

Good soil also:

• Holds moisture for plants while allowing excess water to drain away.
• Drains well without drying out. 
• Provides a slow, steady supply of nutrients your plants need, like nitrogen (N), phosphorus (P), and potassium (K).
• Has a slightly acidic to neutral pH (6.0 to 7.0) to ensure plants can absorb nutrients.
• Provides structure for plants’ roots.
• Maintains lots of air pockets so those same roots can breathe.

In short, good soil makes gardening much easier. You won’t have to worry about problems like root rot, weak growth, poor production, or soil that dries out way too fast. In fact, plants growing in good soil can mostly take care of themselves. 

So whichever method you use to fill your bed on a budget, just make sure it still means you’ll end up with good soil. 

With that in mind, let’s look next at things you don’t want to put in your raised beds.

WHAT NOT TO USE WHEN FILLING A RAISED BED

Saving money in the short-term won’t seem so great if you fill your garden with things that will actually make gardening more difficult. I see gardeners end up spending more money on fertilizers trying to fix bad soil that’s not supporting plant growth. 

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

Things That Don’t Break Down

You don’t want to put anything in your raised bed that doesn’t break down over time. Not only will they restrict plant root growth, these synthetic materials also leach harmful chemicals into your soil. This category includes: 

• TIRES – Tires won’t break down during the lifetime of your garden, but they do degrade. And when they do, they release heavy metals, chemical pollutants,and microplastic dust—not things you want in your soil. 
• PLASTIC – I’ve heard of people filling the bottoms of their raised beds with plastic water bottles. Plastic does not fully biodegrade, but it does leach BPA and microplastics into your soil. 
• STYROFOAM – Styrofoam isn’t great for our health or the environment. 

Gravel or Rocks 

I’ve seen many gardeners spread gravel or large rocks over the bottom of their raised beds. These large, coarse materials can actually make raised bed drainage worse by collecting water after it’s moved through the soil. You don’t want the roots of your plants sitting in little pools of water; it reduces oxygen, causes plant stress, and can even lead to rot. 

Large rocks can also, of course, block root growth and development. 

Vermiculite 

While vermiculite is a naturally occurring resource that’s been processed, studies have found that some vermiculite products, including pre-mixed potting soils, contain low levels of asbestos. 

Contaminated or Sickly Materials

This includes treated wood scraps and building materials that may contain VOCs. While most treated wood is free of harmful carcinogens like creosote, I prefer to stay on the safe side in a garden that will grow food. 

If you’re not sure whether a material has been treated with anything, don’t use it. You’ll also want to avoid any diseased wood. 

Potting Soil

Not only are pre-mixed bags of potting soil expensive, they don’t have the right structure needed for raised beds. Potting soil is also finished breaking down, so if your beds are filled with potting soil and nothing else, they won’t be able to support those beneficial organisms like fungi and bacteria. 

Use only natural materials in your raised bed. When these materials break down, they’ll add organic matter that enriches your soil. It’s best for your health, the soil health, and the environment! 

Luckily, there are plenty of materials you can use that won’t hurt your wallet! 

5 CHEAP, EFFECTIVE WAYS TO FILL RAISED GARDEN BEDS

These options are simple (and often free!), but they do take several months before they provide the ideal space for planting. Here’s the thing: filling your raised garden bed over time is the best way to save money and build better soil.  

The materials used in these budget-friendly methods will break down over weeks and months, creating that humus-rich soil that’s so great for vegetable gardening. 

1. Hügelkultur

If you have a few months to spare before gardening season, you could give this centuries-old gardening technique a try. Hügelkultur, or “mound culture” in German, involves forming mounds out of organic materials like old logs, twigs, grass clippings, and compost. 

The logs used in this method significantly decrease the amount of soil you’ll need and help retain moisture. Over time, they create a welcoming environment for beneficial fungi. 

Here are the steps to set up soil using hügelkultur: 

1. Start by placing old logs and other pieces of untreated wood at the bottom of the bed. Water the bottom of the bed. 
2. Layer twigs, grass clippings, aged animal manure, and/or fall leaves on top of the wood until you’re within 9 inches from the top of the bed. Water in between each layer. 
3. Top off the bed with a thick layer of compost and topsoil. Water well. 

2. Lasagna Layering

This method, also called sheet mulching, is similar to hügelkultur but doesn’t rely on wood. Instead, you make many thin layers with cardboard, newspaper, mulch, straw, and compost. 

Follow these steps to make your lasagna layers: 

1. Spread plain brown cardboard (tape and stickers removed) across the bottom of the bed. Water well. This layer breaks down slowly. 
2. Cover with layers of twigs and sticks, untreated wood scraps, shredded newspaper, straw, pine needles, mulch, dried leaves, grass clippings, and/or half-finished compost. Water each layer well.
3. Top off the bed with a thick layer of finished compost and topsoil. Water well. 

3. Compost

Compost is considered black gold in the gardening world. It releases nutrients that are bioavailable to plants, improves soil structure, retains moisture, and helps break up clay-heavy soil to increase drainage. 

I use compost as a major component of my soil blends, and I also spread a 2- to 3-inch thick layer of compost over the surface of each bed before every growing season. 

The great news is you can easily make your own compost at home with kitchen scraps and garden waste. You’ll just need a little pile or bin in your backyard. Materials to compost fall into two categories: greens and browns. Greens, or nitrogen-rich scraps, include things like healthy garden debris, banana peels, eggshells, coffee grounds, and grass clippings. Browns, or carbon-rich scraps, include fallen leaves, cardboard, and sticks. 

The ideal ratio of these materials for composting is 1 part green for every 2 to 3 parts brown. This ratio ensures that compost keeps breaking down without becoming stinky and attracting pests. You’ll also want to keep your pile moist, not soggy, and turn the pile every couple of days. A properly maintained pile should give you usable compost in about 6 months. 

👉 Start here with our Beginner’s Composting Guide. 

Cheap Compost Ideas:

If making your own compost isn’t for you, here are some alternate options: 

• Community composting programs 
• Bulk compost from landscape supply stores
• Farmers’ markets
• Community marketplaces like Facebook Marketplace and Buy Nothing groups
• Mycology societies (used mushroom blocks, which are great for composting)

Once your compost is finished (that means it has a soil-like texture and is no longer hot), you’ll mix it into your soil blend to make it go much further.  

4. Leaf Mold

Leaf mold takes something you probably get for free (dried leaves in the fall) and turns it into a loamy compost rich in nutrients ready for your plants to absorb. Like compost, leaf mold improves soil texture and drainage while also helping soil retain moisture.

To make your own leaf mold compost, you’ll gather as many fallen leaves as you can and contain them in a wire cage, compost bin, or even simple garbage bags poked with air holes. After 6 to 12 months, the leaves will have broken down and become crumbly compost you can mix with soil and use to fill raised beds. 

If installing a garden is in the books for you in the near future, start gathering fall leaves now. 

5. Native Soil 

Native soil is the soil you have in the ground, right in your backyard. The big caveat here is you only want to use native soil that hasn’t been sprayed with synthetic fertilizers, herbicides, or pesticides. 

In most areas, native soil is not quite ideal for growing annual vegetables. If your native soil is clay-heavy, you can improve the structure and add nutrients by mixing it with coarse sand and compost. If your soil is sandy, add organic topsoil and compost. 

Keep in mind that if your native soil is filled with weed seeds, you’ll be pulling unwanted plants out of your raised beds for the first year, which defeats one of the purposes of growing in raised beds (no weeds). 

TIPS FOR FILLING A RAISED BED CHEAPLY

Whether you’re building lasagna layers in your garden or waiting on fall leaves to break down, keep these tips in mind to set your raised beds up for success. 

Top with Good Soil

I recommend saving room for at least 9 inches (23cm) of good soil at the top of your raised beds. This gives space for seeds to germinate and roots to expand, all while your organic materials continue decomposing underneath. You don’t want those materials breaking down near the top of your bed, or they’ll take key nutrients away from your plants that are trying to grow. 

Learn how to make my ideal sandy loam soil blend that vegetables love to grow in. It’s got topsoil, coarse sand for drainage, and compost for nutrients and moisture retention.

👉 Use our raised bed soil calculator to determine how much soil you’ll need. (Just use 9 inches in place of raised bed height.) 

Plan Ahead

If you don’t have room in your bed to add 9 inches of ready-to-grow soil on top of the hügelkultur technique or lasagna-style garden, it’s best to wait a few months to plant. That’s because materials like logs, twigs, and mulch pull nitrogen from the soil as they decompose. They also impede the growth of longer-rooted plants like tomatoes. 

I recommend starting your layers in the fall and then waiting till spring to plant. 

Or stick with shallow-rooted, nitrogen-fixing crops like peas and beans. These legumes work with bacteria to make nitrogen more available to plants. 

Refresh

The soil level in your raised bed will sink drastically over the coming year. That’s because all those organic materials are breaking down and settling into rich soil. Be ready to top off your beds each season with a few inches of fresh compost. This will bring the surface level back up, while also replacing used-up nutrients. 

MORE WAYS TO SAVE MONEY FILLING RAISED BEDS

Buy in Bulk

If you’re purchasing soil for the top of your beds and need a lot, consider buying bulk from a landscape supply store or soil yard instead of buying bags of soil from a garden center. You can save a lot of money with a wholesale price. Look for a blend intended for raised beds that’s free of synthetic fertilizers. And bring a truck!  

Don’t Fill Completely

If your beds are over 12 inches tall, you could hold off on filling them completely this first year. Spread organic matter over the bottom and add 9 inches of good soil; that’ll give you plenty of root space for herbs and shallow-rooted veggies like leafy greens, beans, and radishes. Budget for more soil next year. 

Insist on Quality

You’ll save money (and frustration) in the long run by using good-quality soil on the surface of your bed. It can get expensive fixing bad soil—plus, you lose whole gardening seasons! 

HOW TO FILL A RAISED GARDEN BED

The steps to fill a raised bed are simple, no matter the method you’re using: 

1. Spread organic materials, beginning with larger items like logs and moving on to straw, leaves, etc. Water the materials thoroughly after each layer. 
2. Add soil. Aim for at least 9 inches of good quality topsoil mixed with finished compost. Water the soil once you’ve added every 3 inches or so to help it settle. 
3. Top off with amendments. I love mixing Happy Frog All Purpose Fertilizer into the top inch of soil before planting. It’s an organic, slow-release product that contains soil microbes and mycorrhizal fungi for maximum soil health.
4. Plant. You’re ready to plant for the season in your new garden bed!

Pro Tip: If you’re working with native soil from your yard, I recommend testing the pH to see if you need to make further adjustments. 

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You don’t need to go into debt to grow a productive raised-bed vegetable garden. All you really need is lots of organic matter and some patience. You’re building great soil that will nourish your garden for years and give you tons of harvests!