Updated: Mar. 22, 2024
You've built your raised garden beds, but what's the best way to fill them? Follow these tips to create healthy soil for your fruits and vegetables.
Years ago, I built 220 raised garden beds out of stone at my former home, and it required 14 dump truckloads of topsoil to fill them.
This year, I constructed only four for my vegetable garden and strawberry patch. But because there’s no local source of topsoil, filling the beds took a little more creativity. Here are a few tips on how to fill raised garden beds for a healthy and productive harvest.
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Using Different Types of Raised Garden Beds
Because I have a penchant for rocks, stone is my go-to perimeter for my raised garden beds. But in reality, almost anything that holds soil works well.
Wooden construction is popular, but metal, plastic, bricks or even large containers will suffice. Galvanized garden troughs are increasingly popular because they’re easy to set in place and require practically no construction. Regardless of the style, choose the design that works best for you.
Make sure you can reach into the middle of the bed to weed and harvest. For many raised beds, three feet wide and six to eight feet long are practical dimensions. But the height depends on what you’re growing and your personal needs.
To grow most “above ground” crops like lettuce, broccoli and peppers, six inches is deep enough. Root vegetables like beets, carrots and potatoes require at least eight inches. Tomatoes grow best with 12 inches or more of soil, particularly for indeterminate varieties.
One of the nicest features of raised garden beds? It brings the garden closer to you by reducing or eliminating bending and kneeling. This requires substantially more soil, but makes gardening comfortable and easy.
Ensuring Proper Drainage
You’ll need ample drainage in your raised garden beds. This isn’t an issue if the bed rests directly on the ground. But if you choose a large container with a bottom, like a trough, use a 3/8- or 5/8-in. bit to drill holes roughly six inches apart so water drains properly.
Preparing To Fill the Garden Beds
Raised beds reduce weeds. In a garden with a bottom, there’s less concern with them creeping into the vegetables. But for open-bottomed raised gardens, it’s definitely a concern. Place landscape fabric or a couple of layers of cardboard on the ground prior to construction to keep the weeds at bay.
Designing a Soil Mix
Soil is the heart of the garden. If you lack a ready source of beautiful loamy topsoil, you can create it yourself.
Combine a one-to-one ratio of compost and soil-less potting mix to create a light and nutrient-rich medium. When choosing the compost, try to incorporate different types. Look for composted manure or mushroom waste, along with plant-based compost. It’s not imperative, but this broadens the nutrient profile of your soil.
If you can find bagged or bulk topsoil, add up to 20 percent of the volume to the mix. Variety is the spice of life, and this holds true with garden soil.
Depending on the size of your garden, you can premix everything in a wheelbarrow. Or simply dump the bags of compost and potting mix into the garden and incorporate with your hands or a hoe.
Calculating the Amount of Soil
You’ll need to know how much soil to mix before filling the raised bed, so pull out your phone or calculator. Measure the length, width and height, and multiply these numbers together. This is the total cubic feet of soil you’ll need.
Filling the Raised Garden Beds
For beds six to 12 inches deep, fill completely with soil. For deeper beds, it’s sometimes helpful to add other materials to take up space and reduce the overall amount of soil, but it depends on your preference and soil availability.
Here are three top options for taking up space in a deep raised garden bed:
Hugelkultur
Hugelkultur is an age-old practice originating in Germany and Eastern Europe. It involves burying logs and wood debris that gradually breaks down while taking up space. Place these materials at the bottom, then fill the rest of the bed with the soil mix.
Lasagna gardening style
Layer carbon-rich materials like straw or dried leaves with fresh vegetable waste or herbicide-free lawn clippings until it’s at least a foot high. Then add your soil over these layers.
Composting in the bottom
Even just tossing in kitchen waste in the bottom of a tall raised bed, along with lawn and garden debris, allows these materials to compost while using less of your soil mix.
Soil is the secret to successful raised garden beds. By following these tips, you’re creating the ideal environment to enjoy a healthy and productive garden.
