In many parts of the United States, we are experiencing soaring temperatures and drought conditions this summer. It has provided the perfect opportunity to test out some garden water conservation ideas that have been lurking in the back of my mind during previous years of abundant water. One of the strategies that I tried this year was the adjustable-level wicking bed. The success was so great that I am increasing the number of wicking containers on my property ten-fold for the coming gardening season!   So let’s walk through the steps of setting up your own wicking bed.

To give credit where credit is due, I must point to podcaster/YouTuber Jack Spirko of the Survival Podcast. In his podcast episode 3095, Jack details the hows and whys of his wicking bed design. The component of his design that I adopted that makes his design superior to most others on the internet is the adjustable water level mechanism. It’s dead simple, and it counteracts most of the negatives associated with wicking bed gardening. It is true that tiny tweaks can make a huge difference!

What is a wicking bed?

A wicking bed is basically a planting container with a reservoir for water beneath the soil. The name comes from the fact that water from this reservoir “wicks up” via capillary action into the soil above, bringing water to the roots of your plants. You may have seen a small-scale wicking bed in the form of a “self-watering” plant pot in the nursery. The plant is watered by pouring water into the bottom portion where the saucer would typically be in a traditional terracotta pot. We are going to up-size this for productive annual vegetable growth!

Are wicking beds superior to traditional raised beds?

In many ways, I believe wicking beds are indeed superior to traditional raised beds for vegetable gardening. I love a good raised bed! I use quite a few on my property. But for the next few sentences, I’m going to play the role of harshest critic!

If you have ever grown plants in raised beds, you know that regular watering is a MUST. Because of the bed’s position above the natural soil line, water drains away quickly, so the gardener either has to expend a lot of effort to maintain a watering schedule or a lot of money to automate the watering system.

Watering from above is inherently inefficient. Much water is lost to evaporation before it ever reaches the roots of the plant. In addition, for many plants in many climates, watering from above leads to conditions that encourage fungal diseases, such as blight and powdery mildew. And finally, when direct sowing seeds in a raised bed, without constant attention, the upper layer of the soil—where the seeds need constant moisture for germination—can easily dry out, withering those fragile seedlings before they can have a chance to get a strong start.

How do adjustable wicking beds address those issues?

Wicking beds provide a reservoir of water that can meet the plant’s needs for a week or more, depending on the volume of water present. The water is delivered from below, so evaporation is tremendously decreased. Keeping water off the leaves of the plants helps to avoid fungal diseases that plague gardeners like me who live in humid climates. And finally, with the adjustable water level mechanism, the gardener can keep the water level in the soil near the surface for the early days of seed sowing.

How to Build an Adjustable Wicking Bed

There are dozens of wicking bed designs on the internet. Most of them will work! My wicking beds take tips from many of those designs. The most critical component, in my opinion, is the mechanism that can be used to adjust the water level, so I will pay particular attention to that part when we get there.

Materials (Note on pipes and fittings: I have used different sizes on different tubs, and I do not notice any meaningful difference in performance. So the sizes I list here are just the ones that I am using on the wicking bed that I am building as a demo for photo purposes. Please feel free to vary the sizes as needed based on availability of components.) Water-tight container of some type (cattle mineral tubs, IBC totes, stock tanks, etc.), ¾ inch threaded bulkhead fitting, 90 degree fitting, 3/4 inch PVC pipe, 1 ½ inch PVC pipe, French drain, landscape cloth/weed barrier, perlite, soil, drill, hole saw bit.

Let’s start with the container.

To be worth the effort, the container should be relatively large. The smallest of my wicking beds are made from cattle mineral tubs – about 25 gallons or so. Each one successfully contains one tomato plant and 2-3 smaller plants, such as basil and peppers. I also have IBC totes cut in half to form two larger beds. Another recommended vessel is a Rubbermaid stock tank. If I had an unlimited budget, this is what I would choose! The material should be sturdy enough to tolerate a 1 ¾ inch hole being drilled through the side without losing its integrity or strength.

On to the drilling. Only one hole is necessary for this design! Drill a hole to match the size of your bulkhead fitting. This one is 1 ¾ inch. Drill this hole very near the bottom of your container. You will want to be able to drain your bed almost completely from time to time. One of the negatives of wicking beds is the fact that the lower levels of soil are perpetually waterlogged, leading to anaerobic conditions, which are not conducive to healthy soil microbiota. Periodic draining prevents this waterlogged condition by simulating a dry season. My bulkhead opening is placed approximately two inches from the bottom of the container.

Install the bulkhead as shown in the photos below.

The main body of the bulkhead and the sealing washer should be on the inside of the container. On the outside, install the friction washer and the nut. Note that the nut tightens in the counterclockwise direction. The one that I use has the direction marked on the nut itself.

On the outside of the bulkhead, screw on the 90 degree PVC fitting. Dry fit a 3/4 inch PVC pipe that will reach to just above where the soil level will be. This is your water level adjustment mechanism. If you want the water level high, raise the end of the PVC up. If you want the water level low, lower the end of the PVC. The water inside the bed will match the level of the open end of the drain pipe. I will discuss ways to use this feature later.

Cut lengths of French drain pipe to fill the bottom of the bed.

Some gaps are acceptable. Align one of the French drain pipes with the bulkhead to reduce the likelihood of foreign material clogging the outlet.

Add a fill pipe on one side. Cut a piece of 1 ½ inch PVC to the length so that it will stand an inch or two above the rim of the container.

Cover the French drain with two layers of quality weed barrier. I like to place mine at 90 degrees to one another with the excess fabric coming up the sides of the container to overlap the edges. Use clothes pins or similar clips to hold the landscape fabric in place while filling. Tuck the fill pipe between the weed barrier and the side of the container.

Add 4-6 inches of perlite above the weed barrier.

Fill the remaining volume with potting mix.

Fill with water hose using the fill pipe. Set the water level at the desired level using the adjustable drain pipe.

Use and Maintenance

• For planting seeds directly in the soil, it is helpful to bring the water level up to near the soil surface. Keep the water level high while seedlings germinate and send down early roots.
• As plants grow, lower the water level to draw the roots deeper into the soil. Ultimately, the water level should be below the bottom edge of the soil, in the perlite layer. This will prevent the anaerobic soil conditions which destroy healthy soil microbiota and lead to root rot.
• Periodically, it may be beneficial to dry the soil more fully. To do so, simply lower the adjustable drain pipe to ground level. Keep the water at this low level as long as is needed to dry out the soil.

Troubleshooting

• If the weed barrier does its job, the bulkhead should not become clogged, but Murphy’s law decrees that it will occasionally do so… With my smaller wicking beds, it is typically sufficient to remove the external PVC pipe and the 90 degree fitting and use a stick or other implement to clear the blockage. If the blockage becomes too severe, worst case scenario, I simply empty the contents of the bed and start over. With larger wicking beds, it may be worthwhile to design a clean-out access inside the bed itself. In the podcast linked above, Jack describes such a design.
• Limit fertilizer application in wicking beds. High nutrient levels in the water reservoir may lead to excessive and potentially unfriendly microbial growth. Additionally, as water evaporates from the surface, it leaves behind the residual fertilizer, which could potentially “burn” the plants.
• Mulch, on the other hand, is of great benefit in wicking beds, as in most other garden applications. Mulch reduces evaporation, which reduces watering needs even more. It also helps to reduce soil temperature during hot seasons, which can be problematic in container gardening.

Wicking beds provide answers to many of back-yard gardening’s most common annoyances. Watering requirements are drastically reduced in both frequency and volume. Weeding is almost entirely eliminated. Drought conditions become minor inconveniences. Excessive rain drains away in a harmless stream of outflow. Poor soil conditions on your property become irrelevant. Consider using the off-season to build wicking beds for use in the coming year!

What About You?

How does your garden grow? Have you used wicking beds before? What challenges do you face with your in-ground or raised bed gardens? Share with us in the comments, so we can collectively seek answers with wicking beds or other methods!  And remember as you’re setting up your own adjustable wicking bed . . .

You’ve Got This, Mama!