Efficient backyard garden – Part 4: Garden Boxes

garden boxes featured

After destroying the yard and adding irrigation, it’s time to make space for our plants.  While you could carve out rows and plant right into the existing ground, you may not have much success.  Pests, lack of soil control, and poor drainage can make for a frustrating gardening experience.  However, building raised garden boxes is an easy way to prevent many of these issues.

Garden boxes give you control of the soil, allow for proper drainage, and are raised off the ground from common pests and animals.  They are an easy way to organize your garden at a minimal cost.  In this article we are going to go through the entire process of planning, prepping, and building our garden boxes.

Let’s get started!

How big of a garden box do I need? Planning the layout

The first thing you need to decide is how you are going to organize your garden boxes.  If you have a large growing area, it may be tempting to go with the largest box size you can to fill the space.  Might as well maximize your growing potential, right?  However, there are some big downsides to larger boxes you should be aware of before taking the plunge.

Downsides to larger boxes:
  • Expensive: Larger garden boxes require more materials. This includes soil, which might be one of the most expensive up-front and long-term costs.
  • Hard to navigate or reach across: Let’s say you build an 8’x8’ box.  How do you reach the middle without trampling your other plants?  Wider boxes are harder to reach across to care for the plants in the middle.
  • Require more support: The larger your boxes, the more you are going to have to consider adding additional support to prevent heavy soil stressing and breaking your boxes.

Therefore, I recommend you stick to a couple rules when laying out and sizing your boxes:

  • Restrict your reach (width) distance to no more than 4’. This allows you to easily reach every plant without having to move to the other side of the box.
  • If using wood for your boxes, use measurements intervals of 4’ since boards usually come in 8’ lengths at your local big box hardware store.
  • If you do build larger boxes, use keyholes to allow access for hard to reach points.
  • Watered dirt weighs a lot! If you build larger boxes, be sure to add support posts to prevent weight stress or breakage.
keyhole garden box
An example of a keyhole in a garden box to reach interior plants. Photo from www.costco.com

Garden box height

Finally, height is also a major consideration.  The higher the boxes, the less you will have to bend over or squat down when caring for your plants.   This is great for those with back problems or who want to grow deeper rooting plants.  However, this also means more dirt – potentially a lot more dirt.  If your goal is to save money gardening at home, you probably don’t want to go much higher than 12” tall.

 

Picking the materials for building your garden boxes

Now that we have a layout and box size in mind, we can decide on what material we want to use to construct our boxes.

Wood

Wood is the most common low-cost garden box solution out there for most people.  If you can think of a design and have the proper saw, you can easily create it with wood.  Cost effective, light weight, and highly customizable – what more can you ask for?

Small wooden garden boxes are easy to make and highly customizable.

In terms of types of wood to use, cedar is the best you can go with.  It is long lasting and has anti pest qualities that are perfect for garden boxes.  However, it comes at a price.  You can spend a massive amount of money on cedar boards.  Additionally, high quality woods good for garden boxes like cedar and redwood might be hard to find depending on your area.

You can also go with cheaper wood, like the highly prevalent Douglas fir or pine.  While not as resilient as cedar, you will save a boatload up front.  If you live in an area with greater variation of weather – frost, frequent rain, etc., then making the investment in cedar or other quality wood might make sense.  If you live in a more consistent climate, Douglas fir should last for many years without issue.

A note on using pressure treated wood for your garden boxes

If you do any Googling around on types of wood for the garden, you will see a ton of threads and articles recommending not to use pressure treated wood for your garden boxes.  Reason being, up until 2003 the most common preservative used for pressure treating these boards was Chromated copper arsenate (CCA).  The major fear was that arsenic could leach out of the lumber and into your soil.  However, since 2003 the EPA has banned the sale of lumber treated with CCA.  Instead, boards today are treated with a copper based chemical treatment that can help reduce rot and keeps insects away.

The internet being the internet, there are tons of opinions one way or the other on the safety of using these boards in the garden.  You are welcome to do your own research and decide if pressure treated wood is right for you, but I steered clear of using it in my garden mainly due to cost.  Douglas fir was far cheaper for the sizing I wanted and should last a long time in my climate.

Other materials

You can also go with other non-wood solutions.  Cinderblocks and metal sheeting are very popular.  Depending on your area and the availability, you might be able to find these materials extremely cheap secondhand.  However, for most people, these materials are going to be much costlier than wood. The upside is these materials should last for a much longer time.

Downsides other than cost include heat retention and weight.  These materials usually hold heat and keep the soil warmer than their wooden counterparts. Depending on your climate, this can be beneficial, especially if you want to grow hot peppers!  They also weigh a ton.  Moving and arranging cinderblocks can be cumbersome and requires significantly more effort than a few boards of wood.

Other common materials are prefab vinyl or plastic boxes.  While these might be great for niche purposes, you lose a lot of ability to customize your layout with these.

My garden box plan

Taking all of the above into consideration, here is my garden box plan:

Layout: I went with four 4’x4’ boxes.  While I could have gone with longer boxes to better utilize the full space, I wanted to start with more common and manageable 4’x4’ boxes.  I figure this will be a great learning experience that can easily be replicated by anyone reading this series.  Additionally, since we are going to follow the square foot gardening method, one 4’x4’ box gives us a whopping sixteen different planting areas.  Between the four boxes, that gives us 64 growing spaces.  That’s a lot of room to start with!

Material: I went with Douglass fir wood boards due to cost.  Home Depot cut them for me for free, so all I had to do was take them home and screw the boards together.

Prepping the ground below: leveling and pest prevention

Before you build and place your garden boxes, you want to prepare the area you are installing them.  This means two key tasks: leveling the ground and installing some sort of ground cover.

Leveling the ground for garden boxes

First, you need to level the ground beneath your boxes.  This helps prevent runoff when watering.

To do so, use a rake (or preferably, a landscape rake) to level out the ground where you plan to place your boxes.  Check the level by using a level across the middle of a 2×4.  After building and placing your boxes, you can double check by placing your level on top of the box.  Adjust the height by adding or removing dirt to each side as needed.

garden leveling flags
I used flags to mark out the layout and provide easy reference for leveling.

If you need to build on slopped ground, there are a ton of tutorials available for modifying your garden boxes.  This guide on Eartheasy has some great guidance for such a task.

Ground cover beneath your garden boxes

Next, you want to put something beneath your garden boxes to create a barrier between your soil and the ground below.  This helps prevent rodents and weeds from getting under your boxes and into your plants.

Surprisingly, this doesn’t have to be an expensive solution.  If you are on a budget and looking to maximize your value, you can go with cardboard to cover the ground.  Save boxes from Amazon or other online orders and you can quickly get a nice stash of cardboard.  Moving boxes also work great – and is exactly what I used to cover the ground under my boxes.

Who would have thought there was a benefit to helping a friend move and taking their leftover boxes?

layered cardboard garden boxes
Layering down cardboard is easy to do!

If you have serious rodent problems and want to go full out, you can invest in hardware cloth.  This metal grating will keep out the best of digging pests.  Alternatively, you can also use landscape cloth to create a more solidified barrier if weeds are your problem.

Either way, try and extend your ground cover beyond the walls of the box for a good seal.

Tools required for building a garden box

Now that we have our materials ready and ground prepped for installation, we need to build our boxes!  The tools required for assembling your boxes are going to depend highly on the size and materials you chose.

garden box tools
Tools for building the garden boxes!

Assuming you are using precut boards of wood, a box of outdoor water-resistant screws and a drill are all you need.    You can get fancy with sealants if you want to prevent rot long-term, but they aren’t required.

If you want to go super cheap you could use nails and a hammer.  However, your final boxes won’t be as secure as using screws.  If you put a ton of dirt into a larger box, you could have the nails push out from the boards.

Building the garden boxes

Building the garden boxes is a fairly straightforward process if you are just creating square boxes.  Lay out the boards in the pattern you want to build, screw the sides together, and you are done.  I recommend using 2-3 screws per side for a solid hold.

Fairly simple: line up the sides and drill!
Final box placed on cardboard barrier.

Garden box cost breakdown

So how much did our garden boxes cost?  Let’s find out:

Item Price Quantity Total
Douglas fir 8’ board $7.72 8 $61.76
Deckmate screws 3.5” 5 lbs box $25.61 ~0.17 $4.44

Note: Huge box of screws purchased to use in other projects.  Costs reflect this project.  12 screws used for each garden box, 48 screws used out of an estimated 277 total.

Total spend on garden boxes: $66.20 (or $16.55 per box)

Interestingly enough, I was searching through Amazon for less DIY-centric garden boxes and came across this kit.  A 4’x4′ garden box made out of cedar prime shipped for around $40.  While it is over twice the cost of our simple build, this may not be a bad deal for people in remote areas that really want cedar or those too lazy to go to the hardware store.

On the plus side, it does show the cost savings of going the cheap route I suppose!

Check that out!  Our boxes are installed and ready to be filled with dirt.  That’s exactly what we are going to do in our next article!

Continue on to part 5 – filling your garden boxes with soil (coming soon)!

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