One of the most common questions our customers have is, ‘How deep should my raised garden bed be?’, and for good reason; with lots of different options to choose from, it can be hard to know what’s right for you. We’re here to answer that for you today.
By using raised garden beds, you can tend to them without having to bend all the way down down and hurt your knees and back. They also allow you to expand your garden onto your patio or deck.
Factors Affecting Raised Garden Bed Depth
The height of the sides of a raised bed depends on several factors, including the soil depth that you need for your plants' roots to have space to grow, the growing conditions, and drainage.
Once you decide to create a raised bed or several raised beds, choose a garden bed structure that provides space to allow the roots of your plants to grow. To do this, you should first understand the needs of the plants and vegetables that grow in your raised beds.
The Type of Plants To Be Grown
Plants will not thrive if their root structure needs more space for growth and expansion. This is not as much of an issue if the roots can reach the soil beneath the planter, but we’d always prefer to avoid double digging if we can.
How deep should a raised garden bed be? To find out, research each of the different plants you plan to grow in your raised bed. Take note of the requirements for each plant or vegetable as well as the maturity vegetable size.
We can distinguish between shallow rooting, medium rooting, and deep rooting plants.
You don't need a bed more than 18 inches deep for the following plants and vegetables:
- African violets
- Marigolds
- Pansies
- Many herbs
- Broccoli
- Brussels sprouts
- Corn
- Garlic
- Spinach
- Strawberries
How deep should a raised bed garden be for medium rooting vegetables?
The following popular vegetables require a raised bed over 18 inches deep:
- Carrots
- Squash
- Various kinds of beans
Many large vegetables like winter squash and watermelon require at least two feet of soil depth.
There is no single answer for the question, "How deep should a raised garden bed be for vegetable gardens?" Instead, choose the bed depth that makes the most sense for each of your garden beds. Organize your flowers and vegetables according to their soil depth requirements. For more information, see this chart by Garden Betty.
For raised beds on platforms, it’s best to choose ones that are a little taller than you expect to need in case you underestimate the root depth requirement. It is easier to get adequate depth by adding a few more inches of new soil than buying a deeper bed. If you do opt for a Frame It All composite wood raised garden bed, you’ll be able to stack and extend boards as and when needed! (See our replacement parts)
Climate and Soil Conditions
Placing plants in a raised bed optimizes sun exposure by lifting them out of shady areas. Even lifting them up a few inches off the ground can prevent neighboring plants from blocking their light. Place shorter plants on the South side for sun in the Northern hemisphere.
Drainage and Irrigation
Be mindful of drainage and its effect on plant growth. If your plants only have a few inches of soil underneath them, they could easily become waterlogged. Placing a porous growing medium such as gravel underneath the soil will help it to drain. Bear this in mind and allow extra space when choosing the depth of your raised garden bed.
Can a Raised Garden Bed Be Too Deep?
A shallow raised bed is unhealthy for the roots, but what problems occur if your garden exceeds the best raised garden depth?
A raised bed that is too deep will use more soil and cost more. A raised bed on a platform could collapse if it cannot support the weight of the extra cubic feet of soil.
If you want a taller raised garden bed and your plants don't need a deep bed, you can explore two different options to get what you’re looking for:
- Opt for a raised garden bed with legs and tend to your elevated garden bed, without the extra depth you may not need.
- Place sturdy boxes or other empty containers inside the bed structure and cover them until you reached the garden soil depth your plants need
If you require a deeper bed, consider a garden without a floor that is continuous with the soil underneath it. As long as your soil is soft enough for plant roots to penetrate it, the roots can extend beneath the raised bed structure.
Adjust Your Garden Depth as It Suits You
Of course, your backyard’s layout is going to influence the answer to the question of how deep your raised garden bed needs to be. Including raised garden beds in your landscaping allows you to experiment with height in new ways and frees you from having to follow the contours of your property.
As you add to your outdoor space over time, you may want to make adjustments to your garden beds and their contents to complement one another. Use the heights of the raised beds to manage the height of flowers relative to one another. For example, you could place the tallest plants in raised beds that are contiguous with the ground and place shorter ones on elevated platforms to reduce the perceived height difference from the perspective of passersby.
At Frame It All, you have the freedom to customize over time. Our modular collection of raised garden beds are stackable and extendable, meaning you can adjust your garden as and when you need to
We hope this article has cleared up any questions you’ve had about raised garden bed depth. You can shop from a range of our raised garden beds with the links below: