How to Build a Raised Garden Bed
A DIY raised garden bed can be a great alternative to planting directly into the ground for several reasons. Check out the steps in this piece to learn how to build a raised garden bed.
Choose Raised Garden Bed Size and Location
Lawn perimeters are often already filled with trees and perennials. Plus, they may be in the shade or lack space for what you want to grow.
A raised bed allows you to control what kind of soil you work with, keeping it weed-free and giving you a chance to make a prime growing substrate full of organic material, with enough space for plants to grow deep roots.
Frames also help keep things ordered and tidy, especially if you build multiple beds for different plants. Adding nets or caging makes it especially helpful for deterring hungry pests like rabbits, birds, and squirrels.
The first step is always site location. Sunny spots are generally the best for growing edible plants and flowers. Once you've decided what you want to grow, and how much space you need, you’ll know the length of boards to purchase.
This doesn’t have to be exact, but if you want a basic 8x4 foot bed, you’ll need to get three 8-foot boards, as the third one will be cut in half.
Choose a length so that you only need to make one cut for the smaller ends of your bed. Hardware stores usually have cutting services if you don’t have a saw. This is why an 8-foot by 4-foot, 4-foot by 4-foot, or 10-foot by 5-foot layout works, for example. Any bigger and you won’t be able to access the plants.
A minimum depth of twelve inches is recommended, but it depends on the plants you intend to grow. You can always layer boards to get a deeper bed.
Prep the Site
If the site you choose has grass or weeds, you can cover the area with tarp, cardboard, or newspaper for a month to prepare the earth.
If you're moving on a faster timeline, just dig out any grass or weeds, so they don't compete with your plants, then loosen the soil with some light tilling.
Opening an area like this will allow your plants to send down roots and access nutrients and water.
Saving Money on Garden Bed Materials
To save money on a garden bed, you can use whatever material you have around for the sides. It doesn't have to be new lumber, or even wood at all, as long as you can attach it to form a cohesive structure.
If you have yard waste available, you can fill in some of the area with old sticks and cuttings to create a hugelkultur layer. As this material decomposes over the years, it will provide nutrients for your plants to consume, basically acting as free fertilizer.
Building Raised Garden Beds
Once you’ve got a clear dirt patch, you can assemble your boards. Cedar, redwood, and juniper are among the most resilient varieties, so they'll last longer than alternatives like pine. On the other hand, they're more expensive.
Safety Note—Don't use treated wood for garden beds. It can leach leech dangerous chemicals into the soil.
Step 1 - Measure and Mark the Wood
Use a tape measure to locate the center of an eight-foot wooden plank. A cedar plank is a good option because this type of wood is resistant to rot, even when exposed to water.
Mark the center with a pencil in a straight line. If an eight-foot plank size doesn’t work for you, you can easily adjust the size to suit your needs.
Keep in mind that the bed should be at least a foot deep but no deeper than four feet. Using the eight-foot planks described in this tutorial creates a rectangular bed, but you can adjust as needed to create the best shape and size bed for your space.
Step 2 - Cut the Plank
Cut your plank in half with a circular or hand saw. Cut down the line that you measured and marked, leaving you with two four-foot planks.
Step 3 - Set Screws or Nails
Use your tape measure to mark three-quarters of an inch from each end of your planks. Using a drill with a Phillips head bit, sink the screws partially into the end of each plank where marked.
There should be three screws placed three to nine inches apart from each other across each end of the plank. Do this on each end of your planks.
Step 4 - Attach Sides (and Optional Posts)
Hold one plank on its side and match another one up to it at a 90-degree angle so that the screws are facing the end of the long, eight-foot plank. Use a drill and Phillips bit to secure the two planks together with the screws.
For extra stability and an optional decorative touch, you can include fence posts at the corners and attach both joining sides to these.
You might want to give these posts a deeper spot to sit by shoveling out some dirt underneath each of them.
Otherwise, you can just connect the sides directly to each other.
Step 5 - Square Corners
After all, sides are attached to create a rectangle (or the desired shape), use a carpenter's square to line up the corners at 90-degree angles, then use screws to attach them.
Step 6 - Repeat Process at Other End
Repeat this process at the other end to complete the rectangle shape.
Step 7 - What to Put on Bottom of Raised Garden Bed
Place your bed on a flat surface in your yard. You’ll also want to choose a spot that gets good sun.
Remove any debris that exists in that area of the yard. Then, use newspaper, cardboard, or old carpet to cover the ground that exists within the bed. Doing this helps to prohibit the growth of unwanted weeds in your garden bed.
You can also lay landscape fabric inside your frame. This cloth will prevent weeds from growing in your garden and taking over your plants. If you do this, make sure there are no spaces between the frame and the fabric.
Place a layer of small stones over the fabric or other cover to create drainage for your bed.
Combine your soil in a wheelbarrow or other large container. Add compost to the soil and use a shovel to mix the materials like you're prepping a giant cake.
Once you have an even distribution, fill the bed with soil, using the shovel to even it out and spread it evenly (a rake can also help with this phase). It should reach about a half-inch from the top of the bed.
The best soil to use in a raised garden is actually a layered process. First, add some compost, either homemade or from the store, and till it into the ground below a bit. Then, add garden soil that is made for growing fruits and vegetables.
Triple mix or blended soils aren't a bad choice, either, but ask what they consist of, and don’t buy just top soil or “black earth,” as this is mainly filler used for dressing.
You want soil that has nutrients but also a good consistency. Potting mix would technically work, but it’s more expensive, and generally used for smaller pots and planters.
Garden soil is usually a little thicker and can hold its shape while retaining water. Top off with more compost.
The best depth for a raised garden bed is 8-12 inches. You want enough room for plants with large root systems to spread, but not so much that it will compact at the bottom, impairing drainage.
Optional Step - Drill Drainage Holes
The dirt in a raised bed can get compacted and clogged at the bottom. Without drainage, your plants can suffer from root damage, and your wood can rot.
To help prevent this, you can drill quarter-inch holes toward the bottom of each side, both in the centers and toward the corners.
The extra ventilation can lead to better plant growth, since the roots will have better access to oxygen in the soil.
What to Plant in a Raised Bed
Companion planting works well in raised garden beds, so look to combine mutually beneficial species.
For example, tomatoes and basil go well together, a row of marigolds will keep pests away, and taller plants will shade cooler crops like lettuce and kale. Keep plants together that have similar water and light needs, as well.
Herbs like rosemary and lavender prefer dry, arid, sunny locations and don’t want consistently moist soil, whereas tomatoes and peppers are thirsty plants.
Also, plant shallow-rooted crops together in smaller beds, as things like lettuce and herbs only need about six inches of soil, but plants with deeper roots like tomatoes, blackberries, carrots, and squash will do best in twelve to eighteen inches.
Raised beds are an excellent place to grow vegetables, including salad greens, carrots, onions, radishes, beets, and other root crops.
You can also grow flowers in your raised garden beds, whether they are perennials or annuals.
Whatever you plant, make sure that you allow enough space between each vegetable or flower for things to grow.
Once all of your flowers and vegetables are planted, liberally water the entire bed. As new seedlings, your plants will require a lot of water to grow.
Continue watering your raised bed on a daily basis to ensure that your plants grow well.
Protecting Plants in Raised Garden Boxes
Some vegetables are vulnerable to pests like nibbling bunnies, birds, or deer. Depending on the type of plants you're growing, you may want to consider adding a chicken wire fence of a few feet on each side or even caging off your garden beds completely.
For additional thermal protection, you can build a greenhouse cover for your bed using PVC pipes. You will need enough pipes to create an arch across the width of your frame at four-foot intervals.
Cut the pipes to the necessary length. Attach one end of the first pipe to the frame of your bed. Bend the pipe into an arch over the bed and secure it to the frame on the other side.
Continue the process until there are arches at four-foot intervals secured along the length of your bed. Attach netting between each section of pipes.
A basic raised garden bed can be built in an afternoon and provide a great growing space for your fruits and vegetables.
As things mature, you may need to add some supports or trellises, especially for vining plants like beans, raspberries, and tomatoes. Chicken wire and netting can help deter pests, and a sprinkle of blood meal will also keep some hungry critters at bay, as well.
Take some time to plan your rows, but also keep it simple if need be. You’ll learn something new and interesting each year.
If you'd like to build something a little different, check out our piece 4 Raised Garden Bed Ideas for some alternative approaches.