How to Fill Short Raised Garden Beds

With raised garden beds becoming the format of choice for many gardeners, the topic of how to fill a short raised garden bed is crucial. It is important to choose the right garden soil and the right amendment. The organic material you choose determines how the season progresses.

You probably have a thriving compost pile to help you fill your raised bed. Maybe you want to try filling your raised bed with a garden bed soil mix, or maybe you want to build your own bed using regeneration techniques that rely on a supply of organic matter. Whichever method you choose, we can meet your needs.

Filling a raised garden bed doesn't have to be difficult or expensive, depending on what's around you. Here we discuss how much soil you need and how to fill short raised beds!

What is your short raised garden bed for?

To determine which materials will fill the raised garden beds you place in your yard, you first need to decide what to plant. Most raised garden beds will do well with garden soils specially formulated for them. However, you can add amendments that suit the plants you are growing.

For example, homemade compost is an excellent source of most plant micronutrients. Sphagnum moss can help you retain moisture in your raised bed. Native soil will provide the beneficial bacteria and mycelium present in the soil profile in your area. Mulching with sawdust, grass clippings or leaves to lock in moisture and protect the roots from extreme temperatures can also be a problem.

There may be a raised bed gardening technique you want to try that involves layering organic material before watering your low raised bed garden with soil that the plants can grow on. Consider these things before purchasing filler materials.

How much material do I need?

The material you need for a packed bed depends on the size of the bed you are packing!

Birdie's Original Raised Bed is available through the Epic Gardening Store, and we've done the math for you in every configuration available. You are welcome to use our charts on each bed's page to estimate the amount of soil you need.

However, if you are building a DIY raised bed, here is a formula widely used to calculate the volume of your raised bed and how much soil you need:

Width x length x height = total cubic feet of infill material.

Start by measuring each dimension of the bed in feet. If you end up with a bed that is not measured in feet, round it up as this ensures you have enough soil on hand to fill it!

To illustrate my point, let's say you have a new garden bed that's about 4 feet wide, 8 feet long, and 1 foot deep. The calculation for that bed is simple: multiply 4x8x1 by one and you'll find you need 32 cubic feet. If you're buying soil in bulk, it's 1.19 cubic yards of soil, so you'll want to buy at least 1.5 cubic yards of soil to make sure you have enough fill and have leftovers. (And you'll want the leftover soil to cover other beds or use in containers later! Those who buy bagged soil are usually able to find 1.5- or 2-cubic-foot-sized bags; assuming you're using a 2-cubic-foot bag, You'll need 16 bags of soil to completely fill that bed.

If your bed is 4.5'x8.5'x1'5', getting the same amount of garden soil will get you fairly short. Garden beds should be full, these small spaces can add up quickly, especially when you water the soil and it settles! I highly recommend that you buy enough extra soil to water the garden bed later. When the initial soil settles into place and fills every square inch of space, it will sink many inches into the bed. A deep bed may still have plenty of root space, but you may need to top it off on a shallow bed to maintain a productive garden. A few inches of soil can change the world!

A Word About Planting Areas

Before we get into the details of how to fill a brand new raised bed, let's cover some basic rules of thumb. First, no matter which method you use, remember to provide no less than 8 to 12 inches of soil dedicated to planting. If you're using the original birdies bed, there's some room to work with, as the shorter Birdies beds are 15 inches tall. When using shorter raised beds that are only 8 inches tall, do not use filler material and use the entire space for planting. If your bed is smaller than 8 inches, you will need to dig a trench with no landfill underneath to improve the soil and allow the soil to aerate well enough for roots to grow.

Ways to Fill Short Raised Garden Beds

Let's discuss different ways to fill a raised bed that can help you establish good soil. Of course, there are more ways to fill a raised bed garden than this article, but we wanted to cover some of the most cost-effective methods.

The foundation of many of these gardening methods is that they provide you and your plants with a nutrient-rich and constantly replenished raised bed soil. This means you don't have to do as much maintenance to keep your loft bed filled year after year.

Hugelk Culture

The giant cultivation method is one of the best ways to build healthy soil and save money at the same time. The process is simple. It involves laying the base of a large rotted log, followed by smaller branches, then branches. When layering, you fill the holes between the logs and branches with kitchen scraps, compost, leaves, and sometimes leftover potting soil. You can then plant in fall or spring with plenty of good quality soil.

As the decaying debris beneath the soil surface breaks down, amazing soil is being built below. This rich soil is perfect for retaining water and nutrients in a raised bed garden.

There are a few things to be aware of when you're filling a raised bed with a giant culture. First, a large culture raised bed will require you to keep more soil on hand, as your soil levels will drop a lot during the decay process. It is important to add soil throughout the process. Another thing to keep in mind is to leave at least eight inches of space above the rotting material. This allows you to plant holes deep enough for root vegetables if root crops are your desired yield.

To do this, you'll need to dig a trench around the perimeter of the bed before laying the large foundation logs to allow enough room for planting on it. Place the logs in the trench and layer them, making sure to have an 8-inch buffer before starting planting or seeding.

core gardening

Another awesome organic gardening method for filling raised beds is the core gardening method. The core garden uses straw bales as the main material to fill the raised beds.

Just like the giant culture method, you'll need to dig a trench that's at least a foot deep to provide enough room for the hay, as well as the planting area above (at least 8 inches deep, remember?). Some hay has weed seeds in it, so source wisely. We have a great garden trailer product at the Epic Gardening Store that can be your source of hay.

Then add about 5 inches of organics to the top of the straw or hay. This could be composted manure, organic compost, or waste from a compost bin. On top of this, you'll lay down a soil mix, whether it's bagged soil or one you've developed yourself from peat moss, worm castings, grit, etc.

What you are doing is creating a compost bin on your raised bed. When the material breaks down the beneficial microorganisms, the beneficial microorganisms feed on the organic matter, creating a beneficial relationship between the plant and the soil.

Lasagna Gardening

Another great regeneration method for regenerating filled raised beds is lasagna gardening, also known as the sheet mulch or mulch queen method. If trenching isn't your style or preferred method, you can simply lay down a material that produces fertile soil as it decomposes. This popular gardening method is the easiest because it doesn't require plowing or digging for dirt.

Start by placing the cardboard directly on the ground. This layer should be free of tape, adhesives and most metals (staples and fasteners). So take some time to get these out before putting down the cardboard. Use cardboard that doesn't contain a lot of chemicals or dyes, as these can affect the growth of plants on it.

Then put your loft bed on the cardboard. Then several layers of green and brown stuff. Green matter is living tissue from kitchen waste, compost, and composted animal manure. Brown matter comes from dead matter such as twigs and twigs, hay clippings, and dried shredded leaves.

A thick layer of twigs and branches on top of the cardboard base provides good drainage for the bed. Then apply an organic mulch twice the size of the base. Water the layers and add compost about half the size of the base of the branches. Put a layer of mulch on top and in a few days you should be able to plant directly into the bed.

If you want to develop sheet covering technology further, you can dig deeper into the earth and give yourself more room to work. How much space you have should be determined by the amount of material you are going to use.

Fill the bottom of a short garden bed

I should mention that it's entirely possible to mix and match these methods, or do one of them in part, adding a layer of good soil on top. You still get beneficial microbial content, but at a lower level of regeneration.

If the regeneration method is not available within your time frame, no problem at all. You can layer drainage material obtained at a gardening store before adding good soil for planting. Plenty of material draws moisture away from the soil, providing good drainage for the bed. We mentioned using a layer of twigs under the bed for the lasagna-covered section.

Substrates to Avoid

It's important to avoid non-porous rocks, which can create a water table at the bottom of the bed and create conditions where disease can take root. You want something that breaks down easily and creates a break down base for your bed. This is the source of beneficial soil microbes.

Short frame bed custom mix

Once you've covered your base, it's time to think about what to put in the planting layer of your short raised bed. When you get material, make sure you have enough material to meet the cubic foot parameter of the bed.

Many gardening stores sell raised bed mixes. These are generally suitable for growing most annuals, but you may want to consider amendments specific to your garden. Coir and peat moss retain moisture in the bed while providing drainage. Rice husks are another viable option to aerate the soil and create a lightweight material that earthworms can navigate easily.

Lava is a porous material that works like perlite and vermiculite in raised beds, providing excellent drainage and crafting so you don't have to water it as often. Worm casting is a similar material that is great for short raised beds. These are known to promote better overall growth and yield.

Then, there are small amounts of material catering to specific plants. For example, if you're growing acid-loving plants like blueberries or sweet potatoes, adding additional peat moss, pine needles, and cottonseed meal can lower the pH and increase the acidity in the soil.

Animal manure is great when you need a lot of organic ingredients. Plants that benefit greatly from cow dung include turmeric and ginger. What you want to avoid, however, is fresh animal manure, which can burn plants and contain seeds that can germinate in beds. Make sure your manure is fully composted before adding it.

Replenish your low bed annually

The most basic form of supplementing a short raised bed is to simply add more of the soil mix you know works best for your situation. However, some other methods can do this and provide a better soil profile for the next season's crop.

A small lasagna-style layer can give you a nice variety of nutrients that your existing soil microbes will love. Even a thick, uniform overlay has a similar effect. You can let the mulch break down to provide you with plenty of material for the next season. You can compost over the soil or make a small giant mound that will decompose over the next few months.

No matter which way you decide to go, there are options. It can be professionally made or thrown together as you want, and it can be as expensive or as cheap as you need it to be.