Self watering veggie garden – a DIY guide

Is a self-watering veggie garden really all it’s cracked up to be? In short, absolutely, YES.

Veggie gardens can fail for many reasons such as average soil, lack of nutrients, and poor positioning, but over 17 years working on edible garden projects the number one cause of failure that we see is a lack of moisture. That’s right, water!

If water is the biggest cause of failure then a self-watering veggie garden is the perfect solution.

‘Wicking reservoir’ is the secret to a self-watering veggie garden that works

A self-watering garden box is also known as a wicking bed. Water ‘wicks’ up from the reservoir, ensuring plants have a constant source of water delivered directly to the root zone. This is the most efficient and sustainable way to grow plants.

In essence, wicking beds are a container garden bed featuring a water reservoir under the soil. Like all good sustainable design, wicking beds learn from the processes of nature. In this case the amazing ability of water to “wick” upwards through the soil through in a process known as osmosis or capillary action. By constructing a garden bed with a watertight reservoir under your soil, you can replicate this natural process.

This is the most efficient and sustainable way to grow plants

Tree roots by the water. Attribution: Pam Fray

Why this self-watering garden bed design?

Wormlovers have been designing, constructing and installing self-watering gardens for many years. We have installed hundreds of them in backyards, community gardens, city laneways and even rooftop gardens. Over the years we have developed various different designs and worked through the many details of how wicking beds work. Our design optimises their efficiency, longevity and aesthetics. We are more than pleased to be able to share this knowledge with you if you’re feeling handy and motivated! We can also supply you with one of our own as a kit or fully installed.

The advantages of wicking beds are numerous. They use up to 90% less water and plants access as much as they need, resulting in much healthier plants.

Wormlovers home delivered self-watering garden beds [Melbourne only]

Moreover, because the water is coming from below, plants have much better root development and are therefore healthier and more resilient during heatwaves and other adverse conditions. In many gardens there is a tendency to overwater which can be detrimental. On the other hand, in the height of summer it can be difficult to get enough water into the root zone when the soil is dried out. A wicking bed solves all these issues, and as long as there is water in the reservoir the plant will draw up only as much water as it requires. If your reservoir is adequate, and you mulch well, you will only need to fill up the reservoir once a week even in the height of summer as you are losing almost no water to evaporation. It is all going to the plants!

 

DIY guide to a self-watering veggie garden

If you are building your own wicking bed it’s very important to get the basics right. You can build your bed to any size but the essentials below remain the same.

Step 1: Preparation

These beds are hard to move so it’s best to decide where you want them before you get started. Full sun is best if possible, especially if growing vegetables. Make sure the site is level and of course you have access to water.

Step 2: Choose a container

Theoretically you can use any container or material to make a wicking bed, however it should be robust enough to handle the weight and forces of the wet soil and substrate.  You can also convert an existing raised bed to a wicking bed using the guidelines here.

Step 3: Get the depth right

We recommend 150-200 mm for the water storage (reservoir) in the bottom, and then 250-300mm for the soil on top of the reservoir – so a total of 400 to 500mm. Water will not wick upwards more than about 280 mm which is more than enough for most edible plants.

Step 4: Waterproof liner

 

This is a critical step as you are making your container hold water. You will line the entire inside of the container up to the top. The black liner in the image above is the waterproofing, the green material is to protect the liner from the substrate to prevent punctures.

You can use pond-liner or other tough flexible plastic material such as builder’s plastic however if you are concerned about possible toxins leaching into your soil it is best to use food grade materials.

Check carefully that there are no nails or sharp edges that could damage the liner in the container. To be on the safe side you may wish to place a layer of protective material such as shade-cloth, geotextile or or even old carpet underneath the liner if your container has rough edges. You don’t want any leaks or your wicking bed will fail!

Wormlovers use a tough 0.5 mm polyethylene food and water safe liner (AS/NZS 4020:2005) for our hardwood wicking beds. As shown above, it is wise to place a protective layer of shade cloth or geotextile (see Step 4) on top of the waterproof liner to prevent your substrate from damaging it.

Step 5: Lay the inlet pipe

You will need an inlet pipe protruding above the bed in one corner so you can fill up your reservoir. You can use any pipe, even hose, however using a 50mm diameter PVC water pipe makes it easy to fill and you can easily see the water level. Use a cap to keep snails and mosquitos out.

We recommend adding an “elbow” at the bottom of the inlet and attaching a section of 50mm black slotted “agi-pipe” which sits along the bottom of the wicking bed and allows water to easily flow into the reservoir.

Step 6: Fill with substrate

The substrate is there to support the weight of the soil and yet still allow water to be stored in the reservoir.

You can use sand, broken up bricks, or rocks however we use 20mm scoria as it is lighter than most rock and is porous so allows more water to be stored.

Never use soil or anything organic which will decompose and produce smells and pathogens in the reservoir.

Step 7: Overflow outlet

The overflow outlet ensures water will drain from the bed once the reservoir is full and not waterlog the soil. The overflow should be installed at the point where the substrate meets the permeable membrane holding up the soil – so exactly the level where the membrane separates the soil and substrate.

Drill a hole through the container wall and liner using a 22 mm drill bit. Use a 15 mm threaded pipe secured with back-nuts for your overflow outlet – you can use either plastic or copper threaded pipe, the latter is more durable.

Once installed use silicone around the joins to avoid leaks when tightening the back-nuts on both sides. Some wicking beds have a drain at the bottom so the bed can drain freely in winter, however if you use well-draining soil this shouldn’t be necessary

Step 8: Permeable membrane

You need a layer between the water reservoir and the soil that water can pass through [permeable].

This layer needs to be non-organic so it will not rot. Commercially available non-woven geotextile is ideal and not too expensive. You can use shade-cloth, however as the holes are larger more roots will get through to the reservoir.

Step 9: Add great soil

After all your effort setting up your wicking bed, you will want to use the most productive and nutritious soil available. Don’t skimp on an inferior soil!

As well as having lots of organic matter and a complete range of minerals, it is very important the soil has a well-draining friable structure. Lots of quality compost and worm castings will ensure long lasting productivity as well as aiding the wicking process. Adding perlite will keep the soil light and reduce compaction. Make sure the soil is nice and wet as you add it to the planter, so your seedlings have plenty to drink when you plant them.

Wormlovers grow medium, supplied with our wicking beds, is full of slow release nutrients, humus and microbial activity. This ensures long term plant productivity, health and nutrient density. We blend worm castings, composted food waste and manures, washed sand, complete blend of rock minerals, vermiculite and perlite, ensuring high water retention capacity, compaction resistance and is ideal for most plant varieties.

Step 10: Fill, plant, mulch, eat, repeat!

If you’ve made it this far you’re well on your way to a successful growing season!

Fill the reservoir via the inlet pipe with a hose until water comes out the overflow. Then you’re ready to plant some seeds or seedlings. Once the seedlings are established add some mulch and you’ll be eating in no time!

Self-watering veggie garden – home delivered

We hope this information will assist in setting up your own wicking bed so you can experience how amazingly productive and easy to manage these growing systems are.

Wormlovers can supply long lasting hardwood wicking beds complete with soil and installation for Melbourne customers.

We also supply the beautifully designed Berberis range of plastic self-watering planters that come in a range of sizes and colours, which we can deliver to you anywhere in Australia. And to complete the nutrient cycle, why not couple your wicking bed with a Hungry Bin or Urbalive worm farm and create your own wormy goodness from food waste for your plants.

Wormlovers also custom build and install a range of other wicking bed designs from built-in backyard raised beds to high end corporate designs for public, retail and corporate spaces. Contact us for more details.

Posted in food gardens, rooftop gardens, sustainability, water wise gardening.