9 Steps: How To Build A Self-Watering Planter Box

Two white wooden self-watering planter box full of yellow flowering plants.

Converting ordinary pots into self-watering planters have become increasingly popular these days because they really are that efficient and not to mention, quite easy to maintain.

They serve best their purpose, which is to provide convenience to gardening and help maintain the level of soil moisture the plants require.

These types of planters offer convenience, water efficiency and ensure your plants won’t suffer from dehydration if you often forget to water them or even if you go away from your home for a night or a few days on vacation.

The planter structure comprises two sections; one is for growing while the other serves as the reservoir.

The growing compartment contains a wick that plunges into the reservoir, and through capillary action, pulls the water up to supply the plant’s water requirements.

And for the process to work efficiently, the soil has to be lightweight and well aerated.


How Do Self-Watering Planters Work?

Newly built self-watering planter box built out of corrugated steel with pond liner covering the inside perimeter.
Image by: diy.dunnlumber.com

Self-watering planters, also known as a sub-irrigation planters, are things you’ll surely love if you’re a fan of growing fresh salad greens, herbs, and tomatoes in the summer.

These planter boxes are designed to grow food in areas with remarkably dry, hot weather. It’s a growing container that rests over a reservoir, to draw up water and supply consistent moisture to your plants.

Designs for self-watering planters are endless. They’re easy to DIY using inexpensive and commonly available materials. There are tons of chic commercial options to choose from.

Your plants will surely survive as long as there is water in the reservoir, which is perfect if you are constantly busy or away from your home.

Understanding how this planter works will let you see first-hand why gardening using a self-watering planter has been trending recently.

Here is an in-depth look at how to build self-watering containers, and as you read on, you’ll be inspired to give these innovative planters a try.


9 Steps: Building Your Self-Watering Planter

You’ll need:

Tools
  • Clamps
  • Level
  • Router
  • Hand saw (Miter saw, Hacksaw, Jigsaw)
  • Cordless drill
  • Countersink drill bit
  • Drill bit set
  • Combination square
  • Framing square
  • Stapler
  • Utility knife
  • Safety glasses
Materials
  • 6 Pcs. of 12′ cedar 2x6s – for the planter’s sides and ends 
  • 3 Pcs. of 12′ cedar deck boards – for the planter’s floor 
  • 2 Pcs. of 10′ 2x4s – for the top cap 
  • 1 Pc of 8′ 2×4 – for joists 
  • 4 Pcs of 8′ 2x2s – cleats 
  • 4-inch diameter perforated drain pipe with sleeve 
  • Pond liner – you can use rubber or poly 
  • Exterior screws 
  • Soilless potting mix 
  • 1/2″ vinyl tubing – for drainage 
  • 1″ CPVC – fill tube
Step #1 – Assemble the Back Ends
  • Get the straightest 2x2s for the corner brackets.
  • Assemble the square by aligning the parts.
  • Use 1/16-inch washer spacers as you leave gaps between the planks to allow adjustment when assembling the box.
Step #2 – Screw the Box Sides
DIYers begin to screw a planter's wood support.
Image by: familyhandyman.com
  • Keep the boards straight using a clamp as you screw the back ends.
  • Ensure the top boards are straight to make the cap fit tight perfectly.
Step #3 – Assemble the Box
  • Clamp the edges.
  • Press firmly with the other hand as you screw each plank.
  • Assemble all the parts tightly.
Step #4 – Determine Where to Establish Your Planter Floor
  • Mark for the decking joists to determine where to establish your planter floor.
  • Remember to consider your soil depth, the flooring thickness and the height of the drainpipe when determining the planter box exact measurement.
  • Add an extra inch in your measurement so the soil level will sit an inch below the rim of the self-watering elevated garden.
Step #5 – Attach the Joists
  • Fasten each end in place with the screw.
  • Repeat the process when you place the center beams.
  • Create a notch to fit your deck boards firmly around the vertical support.
  • Use a 2×2 horizontal cleats to establish stable support to all the planter ends and another 2×4 for the center joists.
Step #6 – Attach the Pond Liner
DIYers trimming the excess pond liner covering the inside perimeter.
Image by: diy.dunnlumber.com
  • Attach the rubber pond liner around the perimeter inside the planter using the staples.
  • Attach the liner correctly and prevent tears. A tear will cause a water leak that might damage your planter.
  • Trim excess pond liner to secure and keep the raised bed planter tidy.
Step #7 – Get the Drain Pipe and Fill Tube in Place
Placed the three black perforated drain pipes on the planter's floor with a two-towered water bottle fixed as a fill tube.
Image by: insideurbangreen.org
  • Get the perforated drain pipes about 6ft long into the floor and space evenly.
  • Secure the ends tightly or tuck a fabric around the edges against the planter to keep the potting mix from getting into the pipes.
  • Fill and secure the potting mix around the pipes to keep them in place.
  • Create a hole and fasten the fill tube at the top end of one of the drain pipes.
  • From there, the water will flow into the drain pipes down into the perforated tubes.
Step #8 – Establish a Drainage Hole
Newly drilled drainage hole at the back ends of a planter box.
Image by: diy.dunnlumber.com
  • Drill a drainage hole opposite your fill tube at the outside end of the elevated planter just above the pipe.
  • Fix a vinyl tubing to the drainpipe through the drainage hole and lodge to the fill tube at the top of the drainpipe.
  • Make sure the fill tube is long enough to poke out the soil surface once your raised bed is planted.
  • One fill tube is sufficient for the water to flow into all the drain pipes.
  • Extend about 2inch in vinyl drainage tubing out the planter’s side.
  • It is overflow drainage that drains excess water away.
  • This helps keep the water moisture consistent as long as the reservoir is full.
Step #9 – Start Planting
Freshly transplanted flowering plants in a newly built self-watering planter box.
Image by: instructables.com-Pinterest
  • Fill the planters with growing media.
  • Start planting, and when done, fill the water through the fill tube.
  • Allow water to fill down the drain pipe reservoirs until excess water runs out of the drainage hole.
  • The water will gradually leak out of the perforated pipe to the soil, and eventually up into the portion the roots can reach.
  • Monitor the planter and see how long the soil stays moist.
  • This way, you’ll know the exact cycle of when to refill the water to keep your plants hydrated.
  • Fill the drain pipes storage when you find the soil dry about 2-3 inches below the surface.
  • It usually takes about 2-3 times of refilling water the entire summer.
  • Add mulch to prevent weed growth.
  • Enjoy growing greens and herbs until the first frost.

6 Advantages of Using a Self-Watering Planter Box

Newly transplanted vegetable seedlings into a wooden self-watering planter box.
Image by: foodretro.com

Self-watering containers are a must-have if you love gardening but deal with soil limitation issues, not at home often, live in a hot or cold climate, and most of all, if you’re a forgetful gardener.

This gardening method is perfect if you want a planter that will enhance the aesthetic landscape of your garden and add style to your home, aside from providing homegrown produce for your family.

1) Having Your Planter on Wheels

Building the self-watering raised bed garden on wheels will allow you to move the planter around effortlessly.

The advantage of building your planter boxes is that you can structure them to fit the size of any available space you want them to be located in.

You can locate them in a unique position to get adequate sunlight the plants require without worrying about the possibility of dehydration.

Additionally, you can tuck them into unutilized spaces like a fence line or garage wall.

However, always consider the weight of the planter box when added with soil and growing plants to ensure your project can accommodate the overall load.

You can use them to start transplants from seeds, rooting cuttings, or holding plants temporarily until you find them a permanent location.

This gardening method can inspire everyone to garden, even in places thought impossible.

2) Self-Watering Boxes Prevent Overwatering

The benefit of using a self-watering planter is not only to make sure your plants don’t suffer from dehydration, but also the raised bed is intended to provide your plants with water without the danger of over-watering.

It also helps avoid the possibility of accidental over-watering, which in most cases, causes root rot. It features an overflow drain, allowing excess water to drain away without harming the plant’s roots.

Succulents, cacti, and some other plants prefer to dry out between watering, and should not be grown in the self-watering containers. Herbs like rosemary and flowers like nasturtium also thrive well without the need to water regularly.

3) Self-Watering Containers Majorly Conserve Water

Water consumption, particularly in summer, is a constant concern for gardeners because it can cost you an ample amount.

Adding mulch to larger self-watering containers outdoors helps conserve water by preventing soil from drying out. Besides, mulch makes the planters appear aesthetically pleasing.

Conserving water is one of the many benefits a self-watering planter offers. The trapped water in the reservoir cannot evaporate with the thick soil covering it, making the possibility of manually watering considerably lower.

It helps retain a healthy environment for growing, even with the most thirsty crops like strawberries and dwarf fruit trees.

4) Everyone Loves Worry-Free Vacations

Investing in self-watering planters will allow you to have peace of mind without worrying about watering your precious plants.

This kind of planter offers a simple way to have a hassle-free, beautiful garden without the need to ask someone to look after your plants, particularly if you have a busy lifestyle, business trips, or you’re on vacation.

5) Promotes Healthy Root Growth

Another beneficial feature a self-watering planter offers is a consistent supply of water the plants’ need.

It helps stimulate roots to grow and establish. Sturdy root systems produce larger stems and branches, resulting in lush foliage, more blooms and quality fruits.

6) Self-Watering Gardens Help Prevent Diseases

Most plant diseases love and thrive in moisture and overhead watering, particularly at night, which is one of the many causes of plant disease spread.

Overhead watering is best done in the morning when the sun rises, so the leaves dry quickly, rather than sitting in the moist weather all night.

Some plants, like tomatoes and phlox, are susceptible to fungal diseases if the leaves get wet, and the use of self-watering containers helps reduce the possibility of infections resulting in healthier plants.


5 Things To Remember When Setting Up Self-Watering Planter Boxes

Newly transplanted vegetable seedlings into an elevated self-watering planter box.
Image by: project.theownerbuildernetwork.co

Self-watering planters ensure your plants are getting the right and consistent moisture they need.

Taking advantage of these planters will give you peace of mind, especially if you can only spend minimal garden time out of your busy lifestyle.

However, there are also a few disadvantages associated with them. Understanding both the advantages and disadvantages of self-watering planter boxes will provide you with reasonable expectations.

1) Avoid Using Regular Garden Soil

Avoid adding garden soil when filling growing media into your self-watering planter. Regular garden soil is too dense and can make wicks unable to function correctly, causing your plant’s untimely death.

Finding the right potting mix is the greatest challenge you need to deal with when opting for self-watering container gardening.

A lightweight and well-aerated potting mix is ideal for self-watering container gardening. It provides the right texture to allow capillary action to wick moisture from water storage, to keep the potting mix moist.

The quality of your potting mix contributes a significant role to generate success among your self-watering raised bed garden.

The basic idea is to provide a mix that will efficiently wick moisture up to the plant’s roots.

Ensure your potting mix can absorb water while maintaining the proper aeration your plants require to thrive.

2) Do Not Let The Reservoir Dry Out

The water in the storage of your raised bed planter is only a buffer to avoid plant dehydration and lessens the effort of watering your plants. But that does not mean you can ignore your plants for weeks or more. In short, it won’t automate your garden, giving you the license to neglect them.

Refilling the reservoir when the water level is low is essential, as dry soil will not wick water, making the plants unable to get the moisture they need.

How often you need to fill water on the reservoir of your self-watering planters depends on the plants you are growing and the size of the water storage your container has.

Plants like tomatoes and strawberries love water and consume a significant amount, requiring you to fill up the reservoir more often. The best thing to do is to monitor at first to gauge how much water your plants need for some time.

A self-watering planter features a capability to keep water in place at the root zone of your garden plants. All you need to do is provide the water your plants require.

3) Know Which Plants Are Ideal To Grow

The self-watering container is ideal for annual plants like tomatoes, peppers, corns, carrots, kale, and lettuce.

These plants demand consistent moisture and grow pretty quickly. And when the growing season is through, you can refresh the potting mix for the next planting season.

Tomatoes are heavy feeders and consume nutrients and water too quickly. They also need an ample amount of growing media to reach full potential.

However, in a colder climate, self-watering storage can freeze solid. The planter is above the ground, and extreme cold lessens hardiness. This also contributes to water-logging, causing root death.

Avoid planting garlic in the planter, particularly in the fall or even in summer. This plant prefers drier, well-drained conditions, and placing them in a self-watering container can do them more harm than good.

4) Self-Watering Boxes Are Not For Fruit Trees and Shrubs

Self-watering planters are most suitable for plants that are small to medium sizes. As such, fruit trees and shrubs are best to plant in a regular pot.

Roots of fruit trees and shrubs can grow deeper and bigger which may damage the self-watering planter.

5) Building a Self-Watering Planter Can Be Expensive

If you are looking to live a green lifestyle and are considering setting up a self-watering raised bed, take note that the initial cost can be more compared to growing traditional containers.

I hope not to discourage you from building a self-watering planter you can use to garden with ease, but of course you must note that you need to spend more upfront for them.

It can cost you a significant amount, especially if you’re considering converting or setting up most of your garden pots into a self-watering planter.

However, self-watering planters are excellent investments in the long run. They are sturdy and weather-resistant. They require minimal maintenance from the reservoir up to the planter box itself if you build and care for them right.


Final Thoughts on How To Build a Self-Watering Planter Box

Self-watering planters offer ease of gardening that needs no watering, making your plants thrive even if you have a busy schedule or are often away from home.

It holds perforated drain pipes that serve as water storage, and the amount of water it requires varies on the size and structure of the planter.

The planter consists of wicking material that pulls water up into the roots through capillary action.

It has a fill tube where you can refill when the reservoir needs more water. It also consists of an overflow drainage hole to drain excess water and prevent the possibility of over-watering.

When considering converting your garden pots into a self-watering planter box, remember to use a lightweight, well-draining soil mix. This allows the planters built-in wicks to function correctly and enjoy the planter’s full potential.

The purpose of building a self-watering planter system is to utilize water wisely and appropriately for the plant.

In the gardening routine, it offers undeniable convenience to people who love to grow homegrown vegetables for their family but have minimal time because of their busy lifestyle.

Another obvious benefit it gives is that planning a few days’ vacation away from home is also possible without sacrificing the health of your precious plants.

Overall, investing in a self-watering planter box will not only offer undeniable ease of gardening, but also the system helps the environment by featuring an undeniable ability to conserve water while adding style to your home aesthetically.

Have you tried gardening in a self-watering planter box? If so, I’d love to hear any tips of what works best for you. Please comment below!

About Benita Abucejo

Hi there! My name is Benita Abucejo. What can I say? I truly love spending my days in the outdoors, specifically in the garden. Gardening has always been a strong passion of mine since I was a little girl. It has brought me so much joy and happiness that it is definitely safe to say that I will be a gardener for life. For a period of time, I was able to work with people who are into home gardening and I found it to be quite beneficial to my physical health, as well as my mental well-being. Here at Seasonal Preferences, I am going to share with you my experience and ideas so that you can fulfill yourself with the same satisfaction and happiness. Of course, if you have ideas, I would love to hear those as well! Being creative in the garden can really be quite fascinating so let's share our experiences and be the best gardeners we can be. With that being said, thank you for dropping by and please leave me a comment on one of my posts if you would like to get in touch!

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