How deep do modular raised garden beds need to be?

There are many good reasons why you should add a modular raised garden bed to your landscape or fruit and vegetable garden. Modular raised garden beds are an excellent solution for harsh soil conditions such as compacted, clay, chalk or rocky soils.

They also address limited garden space and add texture and height to a flat yard. They even help deter rabbits and pests. Gardeners with physical limitations or disabilities also find it easier to use modular raised garden beds.

Modular raised garden beds are also the easiest and most efficient solution if you want to have an edible garden. That's why it's no surprise that more and more gardeners are falling in love with them.

However, an important question now is how deep do modular raised garden beds need to be?

How deep should you fill your modular raised garden bed?

A common depth for a modular raised garden bed is 17 inches, as that is the usual height for gardeners. Fill the raised bed with compost and soil to a depth of a few inches below the edge.

One downside to modular raised garden beds under 8 feet is that most vegetable plants need a depth of 12 to 24 inches to develop their roots well. Rabbits may also get into beds that are less than 2 feet tall, and gardens that are 17 inches tall may require the gardener to squat, bend and kneel more.

To know how deep a modular raised garden bed vegetable garden should be, you must consider the root length of the vegetables you grow most often. If the soil under the raised bed is not suitable for plant roots, you will need to create a bed high enough to allow room for the plants.

Plants with roots 12 to 18 inches long include:




Brussels Sprouts



Chinese chives









Plants with roots 18 to 24 inches deep include:












Black pepper

Plants with deeper root systems range from 24 inches to 36 inches and include:








sweet potato

Determine the specific type of fertile soil your modular raised garden bed needs. You can usually buy bulk soil for your yard.

To check the number of yards needed to fill a loft bed, you can measure the depth, width, and length (in feet) of the bed and multiply them. Divide this number by 27, because that's the number of cubic feet in a yard of soil. The answer you get will be how many yards of soil you need.

Note that you may need to add some compost or other types of organic matter to your regular topsoil. Beyond that, don't forget to fill a modular raised garden bed a few inches below the edge to allow plenty of room for straw or mulch.

What is the best design for a modular raised garden bed?

Modular raised garden beds are freestanding garden beds made above natural terrain. Gardeners have found that modular raised garden beds can solve the most common gardening problems.

Sometimes, the soil may contain too much clay or sand, or be too alkaline, which can hinder plant growth. Poor soil aeration due to poor drainage or compaction can also be a problem. Soil quality issues are exacerbated in suburban and urban environments where vegetation and topsoil are removed or buildings are graded.

Modular raised garden beds can improve growing conditions for plants by rooting on poor soil. Soil amendments can be made to provide better growing media for plants, including those that do not grow naturally. Modular raised garden beds preheat earlier in the spring and are less susceptible to intrusion by tree roots and some grasses. The height of a raised garden bed makes it easier to maintain.

If you're wondering how deep to make a modular raised garden bed, it's important to remember that you don't need to be too deep to be effective. Most of the time, 8 to 15 inches is enough. If drainage is a problem or your plants prefer dry soil, you can choose a higher bed filled with porous growing media.

Vegetable beds should be 12 to 18 inches deep. Materials used to decorate a loft bed must be beautiful, durable and stable. Galvanized metal edges give the bed a unique look in the landscape. This also creates the outline of the bed while keeping the soil in place.

This is easy to install and is perfect for bending the edge of the bed. And the galvanized coating is not easy to rust, which makes the modular raised garden bed last longer.

How to Prepare the Ground for Your Modular Raised Garden Bed

The bottom of the modular raised garden bed is open to allow plant roots to access soil nutrients in the ground. During the initial setup of your modular raised garden bed, you will need to double dig soil underneath it. It has to be done once and is easier to do before the loft bed is assembled.

Double digging involves two lengths of shovel blades or a depth of about 24 inches. This is done to remove rocks and other debris that could hinder root growth. This also gives the gardener a chance to check if the soil space has been encroached on by other roots.

For example, nearby trees may extend their roots 50 feet underground in search of available nutrients. The process of double digging creates a reservoir of water and nutrients for the plant's deeper roots.

Double digging also allows the gardener to check the condition of the soil below to determine the best soil amendment to add. For example, if the soil is more clay-like, peat can be used to lighten the soil to improve drainage and provide ventilation.

Enhanced subsoil through amendments

After the plot is prepared and the rocks are removed, add peat moss as needed to lighten the soil. Lime is added to balance the pH of the soil, as peat is acidic. This is also the time to sprinkle phosphate. You can now assemble your modular raised garden bed and fill it with good soil.

After filling the bed with a few inches of top, add compost and manure. Final amendments must be added within a week or two of planting, as you don't want early spring rains to wash important amendments too deep into the soil.