Whether you're a beginner gardener or just new to raised garden design projects, it takes time to develop those green thumbs. But many gardeners resort to deep raised garden beds as the perfect solutions for plant problems and vegetable gardens.
Because a raised bed garden sits above the natural terrain and can be filled with any soil, they are brilliant at letting your plants and vegetable thrive. By lifting roots above poor soil, plants and vegetables have the chance to blossom.
But the question many people ask is, ‘how deep should a raised garden bed be?'
Well, we've got some expert gardening tips for you, so carry on reading.
How deep does a raised bed need to be?
A raised garden bed doesn't have to be majorly deep to do its job. 8 to 12 inches is usually enough for your plants and vegetables to thrive. But in reality, how deep raised garden beds need to depend on a few factors.
For example, you might have a problem with drainage or plants that need drier topsoil. In this case, you may need a deep garden bed filled with more porous soil.
Minimum soil depths for shrubs and vegetables
When considering how deep a raised garden bed should be, you can look online for charts explaining what root depth certain plants and vegetables need to grow. For example, tomatoes grow best with raised bed soil, usually about 23 to 26 inches of soil (60 to 90cm).
In contrast, if your raised bed is no more than about a foot high, then your roots will only extend to about a foot high. A fact that means your growing vegetables may be stunted. But you might still find yourself growing substantial tomato plants.
Can raised garden beds be too deep?
Like I said, optimum raised garden beds usually sit at around eight to 12 inches deep. But that doesn't mean they can't be taller. You can create a deeper raised garden bed if you have mobility issues or poorly draining soil. Simply back-fill your deep raised garden bed with properly draining and porous garden soil.
People with mobility issues often wonder how deep is too deep. Even in this case, figuring out how deep a raised garden bed should be is easy. Go ahead and make your raised garden bed waist or thigh height if you have problems kneeling or bending down.
These extra deep raised garden beds give you easy access, plus plenty of room for deep roots to grow. But remember, extra deep raised garden beds can be costly to build and fill.
Best height for raised garden beds
When you're working out the best height for raised garden beds, you should have a raised garden bed plan in mind. Ask yourself;
- Do you have mobility issues that make it difficult for you to bend or kneel?
- Do you plan on growing plants that require a shallow or deep raised bed?
For example, if you're growing beans or lettuce that do well with less space, you'll need a much shallower space. About four inches (10 cm) should suffice. You can also try out a vertical raised garden bed with ‘shelves' that are about seven inches (18cm) deep.
These shallow raised garden beds are perfect for herbs, baby kale, and lettuces. But as shallower beds have less soil and tend to dry out quicker, remember to water them plenty.
What do you put in the bottom of a raised garden bed?
The bottom of your deep-raised garden bed can be filled with several organic materials.
Some of these materials include;
- Yard waste
- Wood chips
- Grass clippings
- Sticks and twigs
- Composted leaves
You can then place a suitable weed barrier on these materials. This barrier will keep out lawn grasses, especially bermudagrass, and weeds out of the bed.
Cardboard or any suitable weed barrier material will also do great over this organic material. You can then weigh it down with pegs or a few bricks. Then install a weed barrier in-between the edging and the soil for complete protection.
Next, add your good soil or growing medium before planting your vegetables or rich soil. These are cheaper options for extra deep vegetable beds.
Should raised garden beds have bottoms?
Budding gardeners shouldn't only ask, ‘how deep should a raised garden bed be?' They also need to know if their raised garden bed needs a bottom. Generally, even a deep raised garden bed has nothing on the bottom or the top of it. Raised garden beds are just a frame.
If your raised garden bed is sitting on the ground in ideal circumstances, you shouldn't need anything at the bottom. On these occasions, letting the existing soil meld with your raised bed's soil will improve the deeper roots' growth of your vegetable plants.
But there are times when you may want to add a bottom to your raised garden bed, such as when your plants need protection.
You can use soft or hard bottoms in your raised garden beds, such as;
- Hardware cloth such as wire mesh or a screen
- Weed fabric to stop weeds from sprouting without affecting drainage
- Cardboard and old newspaper (another form of weed protector)
Drainage for a raised garden bed
If you plan on using a bottom on your raised garden bed, remember to factor in drainage. Keeping poor drainage away is possible by placing this hard bottom in your deep raised garden bed. In addition, hard bottoms create extra drainage underneath the soil, essential for thriving plants.
When moisture stress sets in, your veggie plant's roots (especially the delicate ones) are susceptible to root rot, damage, or death. Use rocks for your deep raised garden bed to let the excess water drain away from your plant's roots. Otherwise, the soil can eventually settle and become compacted.