Growing plants in containers is a great way to garden. Whether you live in a small apartment without a yard, or you just want to decorate a porch, patio, or front steps, potted plants are incredibly versatile.
However, the main flaw for potted plants is that they dry out fast in hot weather. So, if you are sick of watering your containers every day in the summer heat, we’ve got a solution: self-watering planters.
In this article, I’ll explain what exactly a self-watering planter is, why they are so clever, and how to make one from scratch at home. Let’s get into it!
What is a self-watering planter?
A self-watering planter, sometimes called a sub-irrigated planter or bottom watered container, is a form of growing container that waters plants from below the roots rather than from above. A reservoir full of water is kept below the soil and a wick draws water into the root zone via capillary action.
- Upper container with soil
- Water tank below soil
- Air gap/drainage hole
- Wick to draw water up into the soil
- Fill tube to add water to the reservoir
Think of the upper portion of the self-watering planter as a normal pot with drainage holes. This part is simply filled with an absorbent potting soil for the plant to grow in.
Below the soil is where the magic happens. The soil-filled pot sits on top of a sealed container full of water. This water is allowed to drain out the side through a drainage hole, preventing the bottom of the soil from touching the top of the water.
A small cup filled with potting soil connects the upper soil with the water below. This acts as a wick, drawing moisture up from the water reservoir into the soil above as needed. Other materials can be used as a wick (such as thick rope).
What this allows us to do is to water much less frequently than in a standard pot. The soil of a normal pot dries out as the plant roots absorb the water and transpire it through the foliage above. With a larger reserve of water in the self-watering pot, your plants will stay hydrated longer.
How to make a self-watering planter (step by step)
Instead of using unsightly buckets, we’re going to class this design up a bit. You can use virtually any plastic pot that doesn’t have drainage holes. Look for large planters that are made for flowers and other ornamental plants.
More of a visual learner? Watch our video guide here!
- Large planter pot without drainage holes
- Ups-a-daisy insert
- 1/2″ PVC pipe (length ~2″ taller than height of planter)
- 4″ nursery pot or similar (deep, circular cup)
- 4″ hole saw (optional)
- Get the correct size Ups-A-Daisy insert.
To create a custom self-watering planter, you’ll need to suspend the soil inside your existing container. Ups-A-Daisy is a brand of plant inserts that are perfect for this. Depending on how large your container is, you’ll need to select the correct diameter. Use a size that will suspend the disc about 1/4-1/3 of the way up the planter. In our case, we are using a 14″ plant insert. (Note: Ups-A-Daisy even makes square inserts if your planter is not circular!).
- Drill several 1/4″ holes in the 4″ nursery pot.
Add holes around the sides of the nursery pot to allow the water to penetrate the soil inside. This will act as the wick, drawing water up into the soil above.
- Drill a hole in the center of the insert.
Using a hole saw, drill a hole slightly smaller than the diameter of your nursery pot. You want the nursery pot to hang below the insert without falling through.
No hole saw? Trace a circle using the nursery pot’s edge and drill small holes along the inside of the circle. Then, using a razor, cut the circle out. Be sure not to cut the hole too large or the pot may fall through.
- Drill a drainage hole in the side of the planter.
Place the planter insert into your large pot and make a small mark where it sits inside of the planter. Then, drill a 1/2″ hole about 1″ below that mark. This will allow excess water to drain out of the reservoir.
- Cut and add the fill tube.
Cut 1/2″ PVC pipe to about 2″ taller than the height of your container. 1/2″ PVC fits perfectly in one of the existing holes in Ups-A-Daisy inserts. If you have PVC that is larger, you can simply drill a larger hole in the plant insert to accommodate it.
Tip: Drill 2-4 small holes in the bottom of the PVC pipe to allow water to freely pass through and into the reservoir. This helps to avoid clogging.
- Pack soil into the nursery pot.
Using a light, fluffy soil mix (such as peat moss, vermiculite, and perlite), pack the nursery pot full. Make sure it is packed tightly to encourage a good wicking action. Then, insert the pot into the hole in the center of the Ups-A-Daisy insert.
- Fill the pot with soil.
With the prepared insert and nursery pot in place, and the fill tube inserted, start filling your pot with soil. Use potting soil without any added compost or other organic matter, as this can degrade over time, reducing the soil’s ability to wick up moisture. Compress the soil firmly.
- Add any slow release fertilizer.
If you plant heavy-feeding plants, you may wish to add some slow release organic fertilizer at this time. This can be added to the soil now to avoid having to feed your plants all season long.
- Plant into the soil.
Add transplants to the soil as you would with normal pots. Water them in lightly.
- Fill the reservoir with water.
Using the fill tube, add water to the reservoir below, and initiate the self-watering magic!
While this method may seem complicated at first, once you understand the concept, it becomes much simpler. Part of your container is now acting as a water reserve tank, while the upper part is simply a soil-filled pot.
Add water to the reservoir every week or so, watching the overflow hole until water comes out. With the reservoir full, you can get away for a few nights and not worry about your plants going dry!
Watch the whole setup here (video guide):
Re-using the planter
Self watering planters can be re-used every year! The most important component is the soil media that you use to fill the pot. Like I said, use a light, absorbent material like peat moss, perlite, and vermiculite. Stay away from ground soil, as this does not wick up moisture nearly as well, and won’t work for this type of container.
One thing you will have to do each season is replenish the nutrients in the soil. I like to use an organic, slow release fertilizer, adding about 1.5 cups per cubic foot of soil each year. This is assuming you are growing heavy-feeding plants like vegetable crops.
You can use virtually any type of fertilizer you want, including liquid fertilizers, slow release pellets, and amendments. Avoid adding compost, as this material eventually breaks down and can decrease the absorbency of the soil.
Other types of self-watering containers
Planters are a great candidate for the self watering design, but what are the other options?
I mentioned buckets as a simple example. If your goal is saving money, 2 buckets, some PVC and some rope as the wick is all you need.
Want to take things to the next level? You can create a sub-irrigated raised bed if you want! This is certainly more of a project, but the principles remain the same.
Pond liner can be used to water-seal the bottom, corrugated and perforated drain pipes along the bottom create a wicking action and air gap, with a light potting soil above.
Here is a great video explaining how to create a self watering raised bed.
Storage bins (mini-beds)
For a smaller and simpler variant of a self watering raised bed, you can use storage totes. These can be used season after season, just be sure to use an opaque material (not clear!).
Self watering containers can be a life saver (literally!). If we try to take even a short vacation in the middle of a hot summer, our potted plants could go thirsty. Now, our plants will stay hydrated, saving us time and money.