Building my Wicking Garden Bed
By Raymond Jess
I discovered wicking garden beds when I did volunteer work at the home of a local Master Gardener. She had four big beautiful beds filled with exceptional looking vegetables and I was inspired by the wicking bed concept. After talking with her about the garden beds, I did some research and found a few articles which gave me the basic information I needed to get started on my own garden project.
I was so excited about the possibility of having a wicking garden bed of my own, I put together a diagram of my yard and got started right away. I must say, my finished product turned out better looking than I expected. My plan was for a 4’ X 8’ garden bed. With the help of a good friend and her truck, we were able to get the construction materials home from our local hardware store. It was not an inexpensive project for me, but only because I wanted all new wood even though re-purposed wood would work just as well.
I used 2×12 pine boards, that I stained for color and protection. Because I wanted the bed to be two feet high, I used 4 boards eight feet long, and 4 boards 45 inches long, to make the basic box. For support, I used 2×2 pine boards on the inside corners.
Once the basic box was constructed, and before I put in the liner, I put a base layer of sand in the bottom to make sure no rocks or thorns protruded. Then I put in the liner. Because we live in the southwest desert and I wanted the bed to last, I decided to use heavy pond liner instead of thinner plastic sheeting. The thinner plastic will degrade and leak due to heat.
I drilled a hole for the bulkhead fitting, covered one end of the fitting with shade cloth to keep bugs out. Then I put a 90° elbow on the other side and attached tubing to act as an overflow and water level indicator. Because of our hard water and the build-up of minerals and salt, our beds should be drained and refilled twice a year. The 90° elbow is able to be rotated to facilitate this draining.
The design requires a fill tube so I used 2-inch PVC pipe. I capped one end, cut it to the desired length and put a 90° elbow on the other. I used the remainder of the tube as the vertical pipe which extends above the level of the planting medium and has a cap to keep the bugs out. Several holes were drilled along the length of the bottom of the pipe to allow the fill water to flow throughout the length of the reservoir.
I filled the reservoir to the top of the bulkhead fitting and made sure there were no leaks. Next, I put in a 1-inch layer of 3/4-inch river rock before I laid in the fill tube. Once the fill tube was in place, I continued to fill the reservoir with rock to the top of the lower 2×12.
After the rock was in place and leveled, I covered it with a sheet of shade cloth to prevent the planting medium from seeping down into the reservoir. I filled the bed with moistened potting mix to a depth of about 10 inches. After filling with this planting medium, I attached furring strip inside the of the bed and trimmed off the excess liner. This was to hold the liner firmly in place. The finishing touch was a 3-inch border along the top.
Wicking beds work on the principle of capillary action from the water. Water molecules are attracted to other molecules and can move vertically almost 12 inches. There is also some evaporation/condensation in action in the bed. Even though I was impressed with the wicking garden bed concept, I looked at the pros and cons before making the decision to build two for my yard.
- The bed is 2-feet high making gardening easier.
- The constant supply of moisture at the root level and overflow tube prevent over-watering.
- The bed is drier at the surface so weeds cannot germinate.
- Use 40-50% less water
- I can leave for a couple of weeks without worry because I water less often.
- Can be constructed on any surface
- Minimal loss of soil amendments because they are not being washed away by top watering
- Salt and minerals are not added to the planting medium from top watering
- Difficult for tree roots and grass to penetrate the liner
- I am growing nutrient rich food for my family.
- More difficult to construct than a traditional raised bed with less parts
- More expensive than traditional raised bed
- Some change in the way you maintain your raised bed
- Requirement to drain and refill twice a year.