Self Watering Garden Containers
One of the biggest challenges of container gardening is regulating the wetness of the soil inside them.
Unlike the ground, where excess rainfall will usually sink deep into the soil and away from the roots of your plants, containers don’t have enough volume to handle too much water. That’s why most of them have a hole in the bottom, to allow drainage of excess water once the soil is fully saturated. Most people just pour water onto the container until some starts flowing out the bottom. Takes less judgement but then wastes water, and a proper Green Wizard hates waste. In addition, plants need some air to their roots too, oxygen and nitrogen gas that makes its way into the soil. Just like earthworms, who come up to the surface and then dry out on your driveway, drowning from too much water, soaked soil prevents those gases from getting to the roots.
That lack of soil volume has a flip side, too little soil to maintain decent moisture. Its easy for planters and containers to dry out, often too easy. A hot day with a lot of sun, can leech the water right out of one. So your plants go through a unhealthy cycle of too much water, then too little. That bad enough for flowering plants that are grown just for decoration, but can be doubly bad if you are trying to grow vegetables. This water stress can cause the plant to grow poorly, set fewer fruits and sometimes even if the fruit grows, can cause big problems as they ripen. Tomatoes can split and crack when exposed to too much water at the wrong time.
We want a way to provide our plants water, without over saturating the soil AND to be able to retain water for a longer time.
You often see these described on the Internet as “self watering planters”, but I think of them as planters with the ability to store water for the plant between waterings. They are made with a double container system, usually out of 5 gallon and 2 gallon paint buckets. The upper planter containers the soil and plant, the lower container (in the space between the two) provides a storage chamber for water. A wicking mechanism provides a way to draw water up from the storage chamber as the soil in the upper chamber dries, keeping the soil moist but not saturated.
Why use these?
Rethinking The Way We Garden – Climate in 2026
I have said here before that over the next three decades that I have to live, being 59 and 7-10 years from retirement, that I expect our global climate to dramatically worsen. Our governments are not going to do anything meaningful about climate change. They are too beholden to moneyed interests that would be affected if steps to cut CO2 emissions were done. Basically all you and I can do is find ways to live in a world with weird climate, and hope for the best. I am hoping to buy 3-4 acres in a semi-rural area, about 60 miles outside of St Louis, here in Missouri over the next 5 years but the use of containers for plants is something that could be done in both a rural as well as a urban location. Even the most restrictive housing, like apartment complexes, can be counted on have some space for a few pots or containers. Or a sunny window.
I do not think that climate change or possible political instability or civil war will disrupt the supply chain to the point where you can get no food. I do expect that there may be times where local disruption will cause food shortages. I also expect that as oil and phosphates get scarcer, industrial farming will put out a less nutritious product. Studies show that in an environment of increased CO2 levels plant productivity decreases. Food you get will be less good for you and more expensive. Having a home garden may be the difference from barely getting by or living with some measure of comfort. Learning to grow plants which look decorative and not food, while being a source of vitamins (like Purslane) will be an advantage.
The Midwest of the United States doesn’t face sea level rise but we will certainly see dramatic shifts in the normal growing seasons we have become accustomed to. I am expecting that periods of intense heat will happen during the Summer. Week long heat waves will put tremendous stress on plants as well as cook the ground surface making watering a problem. When rain does come, the increase in global energy will bring heavy rains and possible flooding. Winters will get milder and shorter offering the chance to plant earlier and perhaps harvest before the Summer heat. The changes to the Jet Stream, with dips to the Southern States like Texas due to loss of Polar Ice will give us the occasional massive snow storm, with huge snow falls and frigid temperature.
In such a climate I believe the adaptability of growing our food in containers is the way to go.
Personally I plan on having at one green houses on my property. South facing with a thermal mass back wall, it can provide a growing space throughout most of the year. Adding a roll up transparent roof would allow better sun during mild weather. Using containers would allow you to bring the plants out into full sun during those periods, while allowing you to seek shelter during storms or sudden cold spells.
In the short term though, I wanted to try saving some of my pepper plants by bringing them in before the cold sets in. I had a very good harvest off of the dozen or so plants I put in hanging baskets.
More on that at the end of the post.
The Secret – Wicking Action
We want our plants to have water but not too much water. Simply putting them in pots with soil and then pouring water on top of them will end up with a very soggy lower area, or not enough water at all. That is where “wicking” comes into play.
Wicking is the physical property a liquid has, where it will spread out as far as possible in the space it occupies. Pour water into a bucket of soil and it will slowly equalize the amount of moisture across the entire bucket. Add enough water and once saturation happens, that is the soil is a wet as it can be, then the excess will sit at the bottom. As evaporation happens at the surface, and the soil dries, more water will be pulled upward to equalize again.
You also see this action in candles. The cloth wick pulls liquid wax and sometimes oils up from the candle and into the burning section of the wick. That’s why wicks don’t completely burn down in just minutes but continue to support the flame. The combustion actually takes place in the space just above the wick.
We want to use this action without having our plant roots down in the soggy part. Roots need some air along with water. When they are completely drowned they can rot. So somehow we need to be able to access the water at the bottom without over watering the whole planter.
In researching this project I found many people use a cloth “wick”. They often use rolled up towels or even socks, with one end pushed through a hole in the bottom of the upper container, with enough cloth to lay down in the water of the lower container. The upper part of the cloth then is in contact with the soil and water is drawn up through the cloth and into the soil.
The downside of using a cloth wick is most will rot and disappear in just a few months. If your plant hasn’t grown its roots down through the holes in the bottom of the top container by then, you will not have a self watering planter anymore. You can still water from the top until you find the roots down into the bottom container.
Other people use a plastic container as a wick. It’s drilled with small holes then packed with dirt. It is placed in a center hole allowing it to just touch the bottom of the water chamber. This is the method I used.
Typically these planters are made with two similar buckets, the top one provides a grow space and the bottom one, water storage. Using regular old 5 gallon buckets is the most common, but I have some using 2 gallon buckets. Any two buckets which can be stacked one inside the other will work.
They are relatively easy to make and cheap. I purchased all of my components for this demo but with a bit of looking you can find most of the parts for free. Local restaurants are a good place to find food grade 5 gallon containers. They get much of their bulk food like beans and flour in them.
In this case I purchased these from a local hardware store for about $3. You’ll need two the same size for each planter you make. You will also need a short length of pvc pipe. Most use a 1 inch diameter pipe but I used 3/4 inch because I had some left over from earlier projects. This pipe is used to fill the water chamber. The pipe goes through the bottom of the upper container.
Then you’ll need the plastic container you will be using as a wick. One person I came across used the food containers you get at the deli. Another used empty plastic yogurt containers. What ever you use should have a bottom smaller than the top, or a lip at top. This is to keep the container from slipping out of the hole you cut for it in the top 5 gallon bucket.
You will also need a few tools.
I found that the bulk of the work can be done with a Dremel rotary tool with a small router bit. You’ll use it to cut the bigger holes in the bucket. A hand drill with a 1/4 inch bit, a hacksaw, a X-Acto knife and a half round file are the rest.
Step 1 – Wicking Hole
For the wicking chamber I am using plastic 9 oz cups made by Solo, purchased at the grocery store. The bag had 40 for a couple of dollars.
My buckets had a small ridge on the bottom, so the first thing I did was cut a hole around this ridge.
And then tried the cup through it.
Hopefully you’ve cut the hole slightly smaller than you need. Take a magic marker and trace around the outside of the cut. Put the body of the marker against the side of the cup and it will draw a line about 1/4 of an inch larger than the cup. This will give you a fairly good outline to cut to. Using the Dremel, recut the hole slightly larger. You may have to do this several times, working your way up the cup. You want to be where the cup sits just a little bit above the bottom container. This way when you fill it and put the top container in, the cup won’t push itself out of the hole and let soil drop into the water chamber.
Clean up the hole with the hand file. I put a slight bevel on it, towards the inside of the bucket to better seat the cup. Minor gaps are ok.
I got lucky and for the 5 gallon buckets, cutting the hole until the cup rested on its lip was a perfect fit. For the 2 gallon buckets I didn’t need to be that deep.
Step 2 – Drainage and Watering
You can also see in that photo the next step, that is to drill the drainage holes in the bottom of the upper bucket. This one is a 2 gallon bucket. I drilled two rows of 1/4 inch holes. In the 5 gallon buckets it was three. Space them out but don’t stress too much about perfection. They are there to let excess water drain from the soil if you put the planters outside and it rains, or are watering them with the hose.
When you do this, put the upper container into the bottom one. Hold it up to the light and note where the bottom of the upper one is. About a half inch down from there, drill a 1/4 inch hole. This lets excess water drain out of the water chamber. If you don’t do this, then the bottom just fills with water and your roots rot.
Notice that you have quite a bit of space for that water chamber, perhaps 3/4 of a gallon.
Next, we want to put in the filling pipe. Cut a piece of pvc pipe as long as the two containers are tall, when they are put together (from the drain hole picture). Add a couple of inches so it sticks out and gives you a better access to fill it. Cut one end at an angle
Cutting the end that goes into the water chamber at an angle prevents the pvc pipe from sealing itself on the bottom.
Next take the uncut end, and use it to draw the size of hole you will need. Use the Dremel to cut it out.
You can also take a moment and make a template for the wicking cup hole. Put a piece of paper over the hole and trace the size. Cut it out and you can then use it to get a hole that should just need a bit of clean up with the hand file for your later planters.
Push the pvc pipe through the hole.
Step 3 – Finishing the Wicking Cup
Next you want to put some holes in your wicking cup so water can get into it.
I use the Dremel to make these since I only wanted them to be about 1/8th inch. Go up about two thirds of the distance the cup sits through the hole. Don’t put any holes in the bottom.
Now take all the parts and give them a good cleaning with soap and water. Especially the buckets. Most plastic items will have a thin coating of mold release, a chemical that helps the part separate from the machine that made it. You don’t want this getting into the food you eat.
Once you’ve done this, its time to add some soil.
Step 4 – Fill It Up
For the lower third of the planter I used a mix of 4 parts potting soil and 1 part vermiculite. I wanted the soil in that section to be a bit looser and easier for water and air to move through.
Take the wicking cup and fill it with this mix, tamping it down into the cup firmly.
Put the cup down into the bucket and seat it. Push the pvc pipe down so it touches the bottom of the lower container too. I rotate the top bucket so that the pvc pipe is on the opposite side of the lower bucket from the drain hole, in the theory that when I fill the lower water storage area, new water will push old water out.
Then fill in the bottom of the bucket with the 4/1 mix to about a quarter of the way to the top.
I leave it loose except for around the pvc pipe. Next fill the bucket with potting soil. I only went to about 2 to 3 inches from the top. I may want to add a bit of compost to the container next year when Spring comes and I put them outside.
At this point you are ready to plant.
What Can You Use Them For
Obviously any vegetable that grows tall or wide like corn or squash, is not going to be a good fit for containers. Nor most types of tomatoes, though there are some good smaller and stouter varieties bred specifically for containers that do well.
I’ve tried several plants in these with some success.
I initially tried some large white onions because I had a few extra plants. They don’t do bad but don’t seem to get their full size growing in a container.
This year I tried some smaller bunching onions, called Crimson Forest” from Baker Creek Seeds.
Unfortunately, the deep red color is only skin deep. They did very well in containers.
Micro-Greens are plants of the lettuce, kale and spinach variety (or other leafy green) which are grown with the intention of harvesting them before the plant gets to its full size.
These containers seem to work well for these plants, and will tolerate a very high plant density. You can set aside 4 containers and do a bi-weekly rotation, planting one container ever two weeks. You can get a surprising amount of greens for salads this way. During the Summer months when these plants typically bolt and go to seed, you can prevent this by taking the container inside when you first see a seed stalk form. This will usually prevent other plants from bolting.
Or just trim all of the plants and have salad for a few days, then replant.
The original reason I made some of these self watering containers, was a conversation I had with my local nursery’s head gardener. His words, “Peppers are not annuals, which live one year and die. They are tropical plants who don’t like cold. Put them in containers, bring them inside, and the following year you’ll get a great harvest.”
Hope you are helped by this tutorial. Let me know if you make some and how they worked for you.
Just to add, a five gallon bucket with wet dirt weight ALOT. For most plants, especially microgreens, the two gallon ones work just as well, and aren’t as heavy.
Thank you so much for making this tutorial. It was very well written & pretty easy to understand, especially because you added the photos. I have no idea what you do for work, but you would make an excellent teacher. I am actually an RN, but a teacher at heart, as that is what I have done with all of my patients. You could do quite well writing manuals used to teach various skills. Bravo!
Terrific tutorial, dtrammel. We did something similar with 16″ raised beds on top of our garage (flat roof deck, with a steel beam centre reinforcement.) We put about four inches of coarse gravel at the bottom, then a layer of landscape cloth, then the soil. At the level where the landscape cloth separated the two, we put a drainage pipe through the wall of the bed, that fed into a gutter that made its way back to our rainwater garden supply, so if we over-watered, it wasn’t wasted. It’s worked pretty well over the years, with a drip watering system laid out between the soil and the mulch. This is it, looking its best (early on… 🙂 )
As the deck only gets half a day of sun, a few years ago we put another garden up on a cliff edge with no soil, this time VERY high raised bed – average 36-40″. I was determined to be able to keep doing this despite arthritis and mobility issues, as well as I wanted to grow parsnips… Yes, I know, expensive parsnips, but with rapidly depreciating savings, what the heck? Anyway, partly traded local labour for doing computer work. So this, below, is the new raised bed garden, again with the gravel reservoir/cloth interface in the background one, and a modified hugelkultur experiment in the other. The gravel was getting ridiculously expensive, so I scrounged a bunch of non-coniferous wood scraps (rare in these parts) and put them in the bottom – about 16″ worth – just throwing the soil in on top, so the wood can break down over time. We’ll see how that goes, but so far so good.
I really like the idea of doing this with moveable buckets, as being able to move things around as the sun moves during the course of the season(s) would really add to the growing period. I wish buckets were as readily available up here – they cost rather a lot when I bought them for the deep pantry – but looking for ones that don’t have to be food-safe is probably the answer. One thing I wonder about – does putting soil into the feeder cup tend for it to bleed into the water reservoir over time?
Although we live on the so-called “wet coast”, it’s actually drought all summer, and the summer is getting longer. Our well used to last all year as long as we only used rainwater collection on the garden, but now it fails for about 3 months of the year. We have some big storage tanks to carry us over that period, but climate change is making a difference. So careful watering with a reservoir below is seriously useful.
Anyway, thanks again for this – I’m definitely going to look out for ways to implement the moveable pot idea!
One thing I wonder about – does putting soil into the feeder cup tend for it to bleed into the water reservoir over time?
Amazing set up you have. Love the photos.
Its been my experience after using these for three years, you get very little physical soil into the water reservoir. A little color at the start but once it gets wet a few times, the soil seems to settle.
Dude, you are a stud. Thanks for sharing this info.
Re the soil sifting into the water – thanks for that, good to know, and it’s reassuring that it’s probably not filling up the gravel beds under our landscape cloth too, which I wondered about but wasn’t about to dig it up to find out 🙂
Amazing set up you have. Love the photos.
Thank you! We’ve been here since ’96, and built it all ourselves, bit by bit, so – time helps.
I love the variety of methods you’ve tried – it’s enormously helpful to see different options. You never know when an idea will settle in and start to morph to fit a different circumstance. And gardens are so flexible, they’re fascinating!