Build Raised Flowerbeds - with Darrell!
Updated: Jul 21, 2020
Did you catch Darrell from Prairie Cedar Creations on CBC Edmonton? We've got you covered! Here is a step by step guide on how to create a raised garden!
A raised garden bed is the perfect solution if you’re tight on space but want to grow fresh vegetables or flowers.
Raised beds allow the soil to warm faster in the spring which means you can plant sooner. Raised beds are easier to tend than ground level gardens.
Get a head start and visit your local Garden Centre and pick from our selection of perennial plants, wildflowers, shrubs, and more. Follow this step-by-step guide to create the ultimate raised garden bed.
The bed frame can be as simple as 2x4s on top of the ground, 2x6, 2x8, 2x10, and 4x4 lumber are other options. 5/4 deck boards are not ideal as they can bow outward over time. The size is up to you. A bed that's at least 6 inches high provides ease of access and gives roots plenty of room to grow. A good practice is to base the size on the lumber you purchase. Standard lengths are 8’ 10’ 12’ and 16’. Base the size of your garden bed on these lengths. If you have 8’ boards cutting them in 2’ and 4’ lengths will provide wood for a 2’x4’ bed without any waste.
There are several options for the style of a simple garden box. Open bottom closed bottom and with legs.
The open bottom is the easiest, but beware that over time grass will probably work its way into the box. By using lawn edging and a heavy duty landscape fabric you can greatly reduce the grass problem. The closed bottom can take care of the grass problem, I suggest keeping it a few inches above the ground. To allow for air circulation to help dry out the wood and extend its life. A raised bed with longer legs keeps most of the wood away from ground contact which means it will last longer.
Soil depth should be kept at a 12-in to 14-in maximum. Most plants do not require more than that.
These instructions describe building a 4-ft. by 6-ft. by 11-in. bed with 2x6 cedar lumber.
What Type of Wood to Use:
The wood to use for a raised bed is your decision. Before you choose, give some thought as to what you want to grow, flowers or vegetables. For flowers, any wood will work, but you are planning on growing edible plants you want to be sure not to use toxic materials. Here are some options:
Edible plants and vegetables:
-Cedar is naturally water and rot resistant and a great choice. -Spruce, fir, and pine are suitable materials for raised beds but aren't very long-lasting.
For decorative plants, perennials and flowers: -Pressure-treated lumber has been a controversial topic for many years. The purpose of chemical pressure treatment is to protect wood from rot, decay, and wood-ingesting insects. -Creosote-treated wood is not a good option for vegetable raised beds.
Recycled wood – wood from recycled decks and fences is not recommended for edibles as any paint stain or chemicals used previously are toxic.
Pallets – wood from pallets is often treated with fungicides and insecticides, but there is no way to tell what may have been used so best to avoid for edibles.
Other materials and considerations:
Use fasteners and hardware labeled for decking — stainless-steel or hot-dipped screws. Make sure screws are at least 2 times the thickness of the wood you are using. For a 2x6 board which is actually 1 ½” thick you would use 3 ½” screws.
Butt lumber tightly. Use inside or outside corner posts to add rigidity
Drill pilot holes to prevent splitting when screwing boards
Use wood rated for ground contact when necessary for the project. (note most pressure treated wood is not rated for ground contact)
Safety: Wear gloves, a dust mask, and eye protection when handling or cutting wood.
Dispose of sawdust and waste according to local regulations.
Building Your Garden Bed: For a 4-ft w x 6-ft l x 11-in h garden box you will need: 4 - 10-ft 2x6 boards 2 - 8-ft 2x4 boards 100 - 3 1/2-in brown deck screws
STEP ONE: Cut Your Garden Bed Walls
Measure and mark the length of the walls and cut the boards. Measure and cut 2x4s for corner posts to support the walls. They should be the height of the garden bed wall. You can also cut posts to install along the walls for additional strength.
Tip: For our frame, we cut four 6-ft. boards, four 3-ft.-9-in. boards, and ten 11-in. support posts. You can build this bed with ten 2-in. by 4-in. by 11-in. boards.
STEP TWO: Attach the Posts
Clamp together the boards for each wall. Set the corner posts on top of the wall boards, flush with the ends of the 6-ft. walls and set back 1-1/2 in. from the ends of the shorter walls. Drill pilot holes and attach the posts with screws. If you cut additional posts, attach them as well.
STEP THREE: Connect all the Sides
Drill pilot holes and connect all the sides with screws to form a box. The posts should be on the inside of the bed.
STEP FOUR: Outline Bed
Place the frame in position and outline it with a shovel. Setting up the bed on the ground rather than a hard surface — such as concrete — allows proper root growth and drainage.
Note: A large frame is heavy and unwieldy. You may need a helper when it’s time to move it.
STEP FIVE: Remove Grass
Set the frame aside to remove the grass. Loosen the dirt with a spading fork to help your new plants' roots grow deeply into the ground. Adding a plastic or wood lawn edging will help with grass overtaking your garden box.
Along the inside edge of the edging, dig a 4-in wide by 4-in deep trench. Fill with crushed rock. This will help drain water away from the bottom of the wood, extending its life.
Attach Wide-Mesh Hardware or commercial grade woven landscape fabric
Before you set the bed in place, staple the mesh or fabric cloth to the bottom of the frame. The fabric helps keep weeds out. Mesh allows earthworms in to enrich the soil. As an alternative, you can use newspaper or cardboard to block weed growth from below, but keep in mind that paper and cardboard will rot over time, allowing grass to grow back in.
If the wood isn't rot-resistant, staple heavy-duty plastic along the inside walls before adding the soil.
There are several options for finishing the exterior of the raised bed.
Leave unfinished – this is the easiest option, all wood will turn grey in time, giving you a more rustic look.
Paint or Stain – Paint or stain has the possibility of adding toxins to the soil. When using stain or paint check with your local paint specialty store for the best kind of finish to use on the wood you have selected. Note if using pressure treated wood, it should weather at least a year before finishing.
Varathane type finishes – Varathane type clear finishes will highlight the natural beauty of the wood, but varathane should not be used on cedar as it does not bond well to the natural oils
in the wood. Check with your local paint specialty store for recommendations.
PLANTING & CARE
STEP ONE: Add Soil Fill the bed with a quality mixture of nutrient-rich soil and compost.
STEP TWO: Plant Set the plants in holes and lightly fill in with soil. Keep the soil loose around the plants to allow water to reach the roots.
Tip: If you use container plants, break up the root ball before planting.
STEP THREE: Water The best time to water is morning or evening when less water evaporates in the sun. Check the plant tags for additional recommendations.