How Deep Should a Raised Box Garden Be?

How Deep Should a Raised Box Garden Be?

A raised box garden should be deep enough for plants’ roots to grow without obstructions like hard, compacted soil or large rocks. Usually 12″ is deep enough.

Depth of Raised Box Gardens

If you are creating a raised box garden on top of your soil then 12″ will be deep enough however if you’re building a raised box garden on top of a surface that is not soil, like concrete or a weed barrier then you might need 18 – 24″ in depth. Larger plants like tomatoes, eggplants and peppers have deeper roots and do better with deeper soil.

Deeper raised box gardens also retain water better and provide more nutrients for a longer period of time than shallower boxes.

6″ Deep Raised Box Gardens

A 6 inch deep raised box garden can be used when the ground soil it will sit on top of is either very good or will be amended with compost or a garden soil mix. I have had 6 inch deep raised box gardens and they do very well with amended soil below. I amended my soil with Coconut Coir, composted steer manure and compost. I like Coconut Coir because it soaks up water like a sponge and resists evaporation.

This is how I prepared a 6 inch deep raised box garden. I pick a location and mark off the site by scoring the ground. I then till the soil using a shovel and a claw hammer. The claw hammer helps break up Arizona rock soil, I mean clay. I till the soil about 12″ deep. I don’t remove rocks like some people do because it will help drain and aerate the soil. Rocks are helpful.

I then place the raised box garden on top of the tilled site. I add the manure, compost and coconut coir and mixed it well with the soil and then leveled it off. I then water it thoroughly to get bacteria, microbes and decomposition started before planting seeds. I usually let a garden “initialize” for 2 weeks before planting seeds.

When the raised bed is ready, I plant seeds and then cover them with a thin layer of grass mulch. Now I water regularly.

6-12″ Deep Raised Box Gardens

A 6-12 inch raised box garden can be used when you don’t want to till or don’t want to till very much soil underneath the box garden. Sometimes I just want to loosen up the top soil and add a small bag of compost. This works well with a 8″ or 10″ raised box garden. It doesn’t require much work but still provides plenty of soil depth for larger plants. Carrots do really well in these.

When you select a location, determine if the soil has good drainage. If you have clay soil like I do, you may want to amend the soil with some organic material. Drainage is critical. If roots sit in water too long they will rot and the plant will die. A good amendment is compost.

The 8″ raised box gardens that I built were made from 2×4’s. I bought some untreated Douglas Fir 2×4’s and stacked them 2 high on the sides. It makes a great box garden and very cheap and long lasting too. Did I say Simple?

12″ Deep Raised Box Gardens

A 12″ deep raised box garden is typical. Most raised box garden kits are 12″. I have had a few. This provides plenty of depth of any size vegetable plant or flower and does not require any soil tilling or preparation. Just built it, set it up and fill it with organic material or you can just buy Garden Soil from a Nursery or Home Improvement store. Kellogg’s makes a good one and so does GardenTime.

After setup, I like to let a new raised box garden “setup” or “initialize” before planting. I water regularly and let it sit. This activates or stimulates bacteria, microbes and attracts earth worms. After 2 weeks, I will see a good number of earth worms in the soil. Worms do magical things in a garden. They aerate, loosen soil, eat organic material and produce worms castings. All of this is “Garden Gold”. Now I’m ready to plant seeds.

You can make your own 12″ raised box garden from 2×12 untreated lumber from any home improvement store. They are pretty cheap and will last a very long time. Just cut to length and screw [stainless steel screws] together. Done

12-18″ Deep Raised Box Gardens

12-18″ raised box gardens can sit on top of the ground or on top of your patio slab. These are deep enough where you don’t have to worry about the roots getting obstructed by anything. Carrots are ideal.

The big benefit of having a 18″ raised box garden on top of concrete or bricks is you have total control over weeds, grass and pests. Weeds and grass will not be able to invade it from surrounding soil. It’s also easier to keep rabbits, cats and dogs out of the garden. You can control how much shade and sunlight it gets by moving it or selecting the perfect location before setup. I love patio gardens.

24″ Deep Raised Box Gardens

I love these!!! Why? Because you don’t have to bend over much to pick the ripe vegetables or do maintenance. It really makes gardening much easier. Try a 24″ or 30″ raised box garden some time. You’ll like it.

DIY 24″ raised box garden – buy some 2×12 untreated Douglas Fir or Pine and cut to size [24″ wide by 36″ long]. Stack 2 high on the perimeter. Simple right?

It requires quite a bit of soil to fill a large 24″ or 30″ raised box garden. You can do a 50/50 mix of yard soil and compost or garden soil. This will reduce the cost but still provide an excellent organic soil. This is what I do when filling a large box garden. Another option is to put a 4″ layer of gravel on the bottom for drainage.

Why Use a Raised Box Garden?

Raised box garden offer many benefits over traditional ground level gardening. The main benefit is soil quality. You can create the very best soil for any type of plant enabling you to grow plants that would not ordinarily grow in your native soil. Soil also has a direct impact on plant health, size and productivity. With a raised box garden you can control this.

A raised box garden can also make it possible to control the amount of shade and/or sunlight the garden receives. If you create a ground garden in the yard, you are limited to that particular location. It may receive all sunlight or all shade. A box garden can be built anywhere, even on the back patio. If you need mostly shade for the plants you want to grow then build the raised box garden in a shady spot like under a tree or next to a block fence or on a covered patio.

A raised box garden enables you to control moisture easier. The soil you create determines how well it retains moisture, plus the water will not seep into the nearby soil. Raised box gardens tend to retain more moisture than most ground/yard gardens. This means you have to water less often.

Raised box gardens also eliminate unwanted weeds and grasses. You won’t have to weed a raised box garden or not very much. Weeds can’t invade it from nearby soil or from a heavy rainstorm. Ground or yard gardens always get weeds and grass in them.

Pests will not destroy your raised box garden like they do to a ground garden. Cats love to dig and poop in garden soil. They tend not to climb in a raised box garden though. Wild rabbits won’t find that tend lettuce crop either. Animals always look for the easy way. If it’s difficult, they may not try.

You’ll have less headaches with a raised box garden.