Wicking Beds 3.0
Things I learned about wicking garden beds…
by Team Member: Ray Jess
Listen to his podcast HERE
When I was introduced to wicking beds almost four years ago, I became obsessed. I have built them at home, for friends, and even built a few on contract. I enjoyed giving suggestions and recommendations to anyone who expressed an interest in wicking beds. I planted, cared for, observed throughout the seasons and adjusted for the health of the plants and soil. As a lifelong learner, through observation of the plants and the garden, I learned many things about wicking beds. Here are some of my takeaways so far.
One size does not fit all
The size of the garden bed is important and highly personal. Consideration must be given to the person tending the garden. When planning a raised garden, a good rule of thumb is: it shouldn’t be any wider than twice the arm reach of the shortest person working the bed. In other words – can the shortest person reach the middle comfortably?
Another consideration is the height of the garden. Build the bed to a height that is comfortable for the shortest person working the garden. A friend of mine built a wicking garden bed 3 feet tall because she had back issues, and that worked great for her. She filled the bottom 18 inches of the bed with sand before installing the liner. Additional thoughts are how many people are being fed from the garden, how close to the house should the garden be, and how close is the water supply?
Wicking beds are unique; they do have a few height limitations. The reservoir should be no more than 11 inches deep and the planting medium the same. The science behind this is that capillary action cannot move water upward more than 11 ¾ inches. Here in the desert where I live, because of our heat, it is a combination of capillary action and evaporation which move the water upward. In the early morning, I can see evidence of water moving up in the moisture rings around the base of my plants, this dissipates as the day heats up and the top soil dries out.
Taking a compass bearing
I was asked to build a raised garden bed with a friend. She had decided on the orientation for purely aesthetic reasons based on the view from the house. It wasn’t until months later, during the summer heat, we realized the bed was getting full sun along its eight-foot length. She was having had a difficult time keeping plants alive, especially along the south and west sides. This was right after I discovered wicking beds, so we converted it to a wicking bed thinking the addition of a reservoir would help solve the heat issue. It wasn’t until the following summer we discovered this did not resolve the issue enough. The garden still performed poorly, not because of the summer heat we realized, but due to the bed’s orientation.
Most experts believe the best way to orient garden rows and raised beds in the Northern hemisphere is north to south— with short sides of the garden facing the north/south. This gives the best sun exposure, allows for ample air circulation, and reduces the heat gain to the framing material. The bed we built was oriented east/west; the better orientation should have been… north/south.
Going around the block a few times
Stone blocks do not make a good frame for a garden bed, at least not in the southwest desert. They can add an additional 8” or so to each side of the garden bed, which reduces the actual planting area and can make the center more difficult to reach. On top of that, stone and cinder blocks are a heat sink material – a true negative in hotter gardening zones. They capture the heat of the day and continue to radiate it during the cooler evening hours. The garden does not have an opportunity to cool down using these materials. On the plus side, I have to admit they are comfortable to sit on while tending the garden.
After several years of using them around my yard and for my raised beds, my current garden beds are made from 2 X 12 wood planks. I found really cool and clean looking metal corners online which made my newest garden bed look more attractive than any of my previous builds.
Keeping my cool
In an effort to keep the planting medium appropriately cool, I experimented with 3/8” foam insulation between the wooden frame and the pond liner in on of my wicking beds. And yet when I started recording temperatures in the two equally sized, side-by-side gardens, I discovered the insulation actually held the heat in the planting medium instead of mitigating the heat gain. I believe foam insulation would be a great option in the colder regions, but not for hot zones like mine.
To rock or not to rock
When I built my first wicking bed, I based my design on the beds built by the person who introduced me to the concept. She originally used large river rock in her reservoirs. However, she learned such large rocks did not allow water to move up to the planting medium. So instead I used ¼” river rock which worked well.
After building these beds, I found an article written by Collin Austin stating the use of a rock filled reservoir was not his design, and in fact he indicated the planting medium itself should be part of the reservoir. So, in my next version (Wicking Beds 2.0) built at my friend’s house, we experimented by using a different fill pipe and put the planting medium all the way to the bottom of the garden bed. The wicking properties of this design was excellent.
One pipe is not like the other
Since the wicking bed 2.0 garden was working so well, I changed the internal structure of one of my personal beds to match. We found the 1 ¼” PVC pipe previously used didn’t fill the reservoir quickly, so I changed to the Bend-A-Drain 4” polypropylene flexible drain pipe used in 2.0. It was easy to see how the wider pipe allowed filling the reservoir easier and more efficiently, and we appreciated how it became another way to view the reservoir water level.
A good flush will help.
Water naturally creates a build-up of salts in the reservoir, which I prefer over it building up in the root-zone. This remedy is a semi-annual flush. When I drained and flushed the reservoir that only had planting medium and no rocks however, there wasn’t a void space for the fresh water to move freely. To adequately flush this bed and remove built up salt and minerals, I heavily watered the planting medium from the top to the bottom of the reservoir and out the overflow drain.
This was a waste of water and nutrients, and I hate wasting resources. So I changed the internal structure of the garden bed again by emptying my garden between planting seasons. This time I kept the 4” pipe but went back to the ¼” river rock as the base of the reservoir. I use shade cloth as a separator between the reservoir and the planting medium and reused a portion of the previous planting medium. This change combines the ease of fill, observable water level, and the ability to flush out the rock reservoir. I am much happier with these results.
One thing at a time!
It is easy to fill the garden bed using the 4” pipe. The idea is to fill the reservoir quickly with a moderately high volume of water over a short period of time. However, it is easy to walk away from the garden when filling the reservoir because we always have “something next” to do. Recently, two different friends overwatered by doing the exact same thing; they put the hose in the fill end of the tube, turned the water on and walked away to tend to something else forgetting about the water for an extended period of time. As you can expect, the water filled their beds and spilled over the sides. The ½” overflow tube could not handle the water volume added to the bed so in Wicking bed 2.0 the unsecured sides gave way. Best choice…us a timer on your water spigot.
With water within easy reach, plants can get lazy
I was surprised to realize the plants in my bed developed root balls smaller than I expected compared to plants in other garden methods. Even if a plant is transplanted from a large pot into a wicking bed, over time the roots shrink. Since water is always available to the plant at the root level, the plant adapts to the consistent moisture level and the root ball generally stays around six inches in diameter. During most of the year this is not an issue in our climate. However, when growing summer vegetables with large leaves, the roots cannot take up enough moisture to keep up with the evaporation during the 100+° days. Consequently, the plants look poor during the day but generally recover overnight.
Take notes and grow
As gardeners, the best we can do for our gardens is to love, care for and observe them on a frequent basis. Watch what is happening and, if it is not what you expect, find out why and takes steps to resolve the situation. Take every opportunity to learn and add those lessons to your mental tool box. The things I have mentioned are a few of my lessons learned. Has this article reminded you of something you’ve learned in your garden practice that you would like to share with others? Please add your lesson(s) learned to the comment section below.
About this author:
After retiring from two careers, the Air Force and teaching, Ray pursued his love of food by graduating from the Phoenix Art Institute with a certificate in Culinary Arts. The highlight of his culinary experience was working as a chef for the 2007 Super Bowl at the University of Phoenix Stadium. Natural extensions for this self-proclaimed foodie were the completion of his Master Gardener training and his Certificate in Permaculture Design.
A love of fresh foods and herbs kept him gardening for the last two decades. During a volunteer component of his Master Gardener training, Ray discovered wicking garden beds. A man of curiosity and a seeker of ways to do things more efficiently, he embarked on a research project leading him to the Father of Wicking Beds, Collin Austin. As a result of Ray’s research, his backyard garden has evolved from rows of crops in a plot of ground, to raised beds, to grow-buckets and wicking beds. He is currently keeping his eyes open for the next great idea to perfect his garden, so he can keep giving his family, friends, and neighbors fresh produce.
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