I wanted a raised bed planter, but the best location in my yard is not close to a spigot for watering. I live in a hot climate and I wanted to find a way to avoid dragging out a long length of garden hose 3-4 times a week to water my garden. I finally settled on building "wicking" raised garden bed. While I still need to pull out the hose once in a while, the number of times is much less. This bed waters from the bottom up, which has many benefits but here are a few key:
- Less evaporation during watering
- Plants are encouraged to grow deeper roots
- Lower water usage because garden draws up water only when needed
This guide will show you the key steps to building your own backyard raised bed garden which needs less frequent watering and encourages deep-rooted healthy plants. The key to this garden is the "wicking" water system built into the bed.
Materials needed for 4'x6' garden.
- Wood for raised bed walls (adjust to fit your garden dimensions)
- 2 2x6x10'
- 2 2x10x10'
- 2 1x4x8' for corners (optional - mostly decorative)
- Galvanixed screws
- 1" PVC for fill pipe and holders for cover supports
- Weed barrier
- Poly liner
- 4" corrugated drainage pipe
- 2 end caps for 4" drain pipe
- drainage rock
- organic garden soil
I purchased everything at my local "big box" hardware store
Step 1: Build Raised Box Container
Begin by constructing your raised container. There are many options for this container, I chose a simple wooden box which is approximately 4' x 6' in size. You can choose to let the wood age naturally, but I decided to put a grey stain on the outside and along the top of the inside. There are many techniques and sites which will show you how to construct the box, and you can probably figure out my approach just from this picture.
Once you have your box located and leveled, dig out some of the soil to form a depression which is below the level of the box approximately 4 inches. (The deeper you dig, the more water it will hold.)
Note: Do not use pressure treated lumber if you will be growing vegetables.
Step 2: Build the Water Containment System.
Next line the depression with a poly liner. I purchased mine from the local big-box hardware store in the paint department. I wrapped the plastic up and attached it to the lower edge of the wooden box with galvanized roofing nails. In the lowest corner, I did not fully attach the plastic at the top, so that water could run over when full.
Once your liner is installed, prepare a section of corrugated drainage pipe. This pipe is 4 inches in diameter and has small holes throughout the pipe to all water to escape. Place a cap on each end of the pipe. In one end, drill a hole and insert a PVC pipe which will be used to fill with water. No need to bother gluing everything together; the purpose is to let the water seep into the rocks anyway.
Next lay the prepared pipe into the depression. I recommend you size the pipe to run the full length of your bed, but it is not critical to loop the pipe as I have done here. The pipe simply speeds up distribution of the water throughout.
Next fill the depression with rocks. Ideally you will fill to the top of the corrugated pipe
Step 3: Cover the Pipe and Rocks
Next, cover the pipe and rocks with a weed block material which still lets water pass through. This barrier will allow water to pass in both directions, but will keep the lower reservoir from filling in with soil. The pipe and the gaps between the rocks is where you garden will store water for when it is needed by your plants. I have weighted mine down with a few rocks to ensure it stays in place for the following steps.
Step 4: Add Extras to Your Bed
Before you add garden soil, it's a good time to add any extras you may want in your garden. I have added 6 small vertical pieces of 1" pipe (3 on each side). I can insert the end of 1/2" pvc pipe into one side, then bend the pipe over the bed and insert into a pipe on the other side. These pipes will then support netting to keep out garden critters; or I can use the supports for row covers to keep out frost on chilly nights.
(You may also notice that I filled the gaps between the slats in my box ... the wood was warped and the gaps were a little larger than I wanted.)
Step 5: Partially Fill and Test
I added about half of the organic soil to the bed and then stopped to test the system. I have added a small tube to the lowest corner where I left the corner of the liner lowered. I also created a small depression which runs under the wooden box. I then filled the water reservoir using the fill pipe until I saw water spilling through the tube and the depression in the soil. (The tube is probably not necessary, but I wanted to be sure the water would escape when the reservoir filled.
I also ensure the system was working by making a small depression in the soil down to the barrier. As it overflowed, I could see water form at the bottom of the depression. This let me know that water was passing through the barrier and into the soil. When the garden soil becomes too dry, the soil will "wick" up water through the barrier. This moisture will be pulled up through the soil so that it can be used by the plant roots.
NOTE: Making sure the water can overflow the reservoir is important. You don't want the water filling up your entire raised bed and drowning your plants.
Step 6: Fill the Bed With Soil
Now that you are certain the system is working, you can finish filling your raised bed.
(That's my beagle, "Snoopy", photo bombing my Instructable.)
Step 7: Start Planting!
Start adding plants! You may still need to water newly planted seeds until they germinate, but once established you should only need to water occasionally. You can check the water level using your fill pipe by using a dowel rod as a "dipstick".