How Deep Should Your Raised Garden Bed Be? Find Out Here

Raised garden beds are a great way to grow your plants if you want to have more control over your soil as well as to have a good drainage. 

But here’s the thing: the depth of your garden bed is more important than you might think because the it helps your plants grow stronger with better roots and healthier leaves.

Get it right, and you’ll likely see better results. If it’s too shallow, your plants might struggle to thrive. Too deep, and it can become expensive and harder to manage.

And that’s just frustrating, isn’t it?

If you’re unsure about what size to make your raised garden bed, check out our guide on raised garden bed sizes.

This way, you can ensure your bed is just the right depth for what you want to grow.

In this article, I’ll walk you through how deep a raised garden bed should be (depending on what you’re growing) and share simple recommendations to help you get started without any hassle.

The Depth of Your Raised Beds Depends on What You’ll Grow

When you're building your raised beds, the depth mostly depends on what you want to grow.

Shallow-rooted plants (like lettuce and herbs) don’t need a lot of space, so a bed that’s not too deep will work just fine.

But for deeper-rooted plants (like tomatoes or carrots), you’ll need more room for the roots to spread out.

So, before you start building your raised beds, ask yourself, “What am I planning to grow?”

That way, you can make sure your beds are the right depth for the plants you want to put in them.

How Deep Do Your Plants Need to Grow?

I do want to make sure you know how deep your plants need to grow well.

As a reference, take a look at these specific plants (you might want to grow) to guide you in determining the right depth for your raised garden beds.

For Shallow Plants

• Lettuce
• Spinach
• Arugula
• Radishes
• Herbs (basil, cilantro, chives)
• Green onions
• Mustard greens

For shallow-rooted plants, a raised garden bed with about 6 to 8 inches of soil is usually enough.

These plants don’t need much space for their roots to grow, as most prefer to keep their roots near the surface. That’s why they’re perfect for quick-growing crops.

With a shallower bed, you won’t have to manage too much soil, making it easier to keep everything watered. It’s also more convenient since these plants don’t require a lot of depth to thrive.

Watering is simpler too, as the roots are closer to the surface and can absorb moisture more quickly.

For Medium-Rooted Plants

• Carrots
• Beets
• Onions
• Peas
• Herbs (parsley, dill)
• Turnips
• Swiss chard

For medium-rooted plants like carrots and various herbs, you’ll want your raised bed to be around 8 to 12 inches deep.

This extra space allows their roots to grow and spread out. Carrots, for example, need deeper soil to grow straight and healthy.

If the soil is too shallow, their roots can hit hard spots, causing them to twist or become stunted.

The additional depth also improves drainage, which is crucial for these plants.

Better drainage ensures the soil doesn’t stay too wet, providing the roots with the right amount of moisture. It also allows some air in, which helps keep the roots healthy.

So, 8 to 12 inches is pretty much ideal for plants that need a bit more space to grow.

For Deep-Rooted Plants

• Tomatoes
• Beans (bush and pole varieties)
• Squash (zucchini, butternut)
• Cucumbers
• Sweet potatoes
• Peppers (bell and hot varieties)
• Eggplant

For deep-rooted plants, you’ll want at least 12 to 18 inches of soil, or even more if possible.

These plants have large root systems that need plenty of space to spread out and absorb nutrients and water.

A deeper bed not only provides the room they need to grow but also helps keep them stable—especially for taller plants like tomatoes, which can become quite heavy as they grow.

So, if you’re growing these types of plants, ensure your bed is deep enough to support their growth and stability in the long run.

What’s the Best Depth for Most Raised Beds?

So, what’s the best depth for your raised garden bed?

While the depth of your raised bed depends on what you’re growing, here’s a general guideline to help you.

For most home gardeners, a depth of 12 inches is usually recommended. This depth works well for a variety of plants because it provides their roots enough space to spread out while also allowing for decent drainage.

If you want to get a bit more ambitious and grow a wider range of plants, aiming for 18 to 24 inches is even better.

The deeper the bed, the longer it retains moisture and improves air circulation—great news for your plants.

In short, while 12 inches is a solid rule of thumb for most raised beds, going deeper (around 18 to 24 inches) can help your garden thrive even more.

Just consider what you want to grow and choose the depth that will give your plants the best chance for success.

Things to Keep in Mind When Deciding Bed Depth

To help you plan even better, keep in mind a few things when deciding how deep your raised bed should be.

Remember that deeper beds require more soil, which can add up in cost—especially if you’re filling a large area. So, it’s important to consider your budget when planning the depth.

Another thing to think about is how easy it will be to reach your plants. If the bed is too deep, it might be difficult to comfortably tend to your plants, especially those in the middle.

Make sure you can easily reach everything without straining your back.

Also, deeper beds also hold moisture longer, making them ideal for plants that thrive with consistent watering.

However, if you live in a wet climate or tend to overwater, you might want to keep the depth a little shallower to avoid waterlogged soil.

By keeping these points in mind, you can choose the right depth that works for both your plants and your gardening routine.

How to Set Up Your Raised Bed with the Right Depth

Before you start building your raised garden bed, it's important to plan out the details (especially when it comes to the depth).

The right depth really does matter for healthy plants, but there are a few other things you’ll want to think about as well.

Here’s a simple guide on how to set up your raised bed with the right depth (everything from picking the best spot to choosing the right soil mix).

Step 1: Choose the Right Spot

The first thing you’ll want to do is figure out where to place your raised bed. Pick a spot that gets enough sunlight for your plants to thrive.

Also, make sure the area is flat, as this will help with drainage and keep the soil spread evenly.

Step 2: Build the Frame

Once you’ve decided on the location, it’s time to start building. For the frame, you can use materials like wood, brick, or even recycled pallets.

The size of your bed will depend on how much space you have and how much you plan to grow.

When it comes to the depth, make sure it’s suitable for the types of plants you plan to grow (you’ve already figured that part out, right?).

Step 3: Add Layers (For Deeper Beds)

If you're making a deeper bed, you don’t need to fill it all the way with soil.

You can use the “lasagna gardening method” by layering cardboard, newspaper, or even yard waste like leaves and grass clippings at the bottom.

If you want to learn more about it, you may want to check out the advantages of lasagna garden to inspire you to adopt the method.

It will help you create space, aids in drainage, and saves you from having to buy a ton of soil.

Step 4: Add the Right Soil Mix

Once your bed is framed, it’s time to fill it with soil. Use a good mix, such as a combination of topsoil, compost, and organic matter, to provide your plants with the nutrients they need.

Make sure the soil is loose, not compacted, so the roots have plenty of room to grow.

If you need tips on how to fill your raised garden bed properly, check out this guide on how to fill raised garden beds.

Step 5: Level the Soil and Put Mulch

Once your bed is filled, lightly rake the soil to level it out. Add a thin layer of mulch on top to help retain moisture and prevent weeds from growing.

Step 6: Water Them

Consider how you will water your plants.

A simple drip system or soaker hose can make watering more efficient, especially if your bed is deep and you want to ensure water reaches all parts of the soil.

Step 7: Get Planting

Now your raised bed is ready for planting! With the right depth, quality soil, and proper planning, you’ll be all set to help your plants grow strong and healthy in your raised garden beds.

Happy building and growing!

Frequently Asked Questions (FAQs)