It seems self-watering containers are all the rage. From super, high-end, fancy planters, to DIY planters made from buckets and plastic boxes, you can find one to work with your price range and style. There are a vast number of options out there and you can even make your own for not much money.
The advantages of self-watering containers are numerous and they can be the best way to grow some plants--particularly vegetables. By providing a consistent level of moisture directly to the roots of plants, self-watering containers can increase plant health and yield. Probably the most common mistakes gardeners make--even highly experienced gardeners--is to over-water plants. With a well-designed self-watering container, this won't happen. The plants will get just the amount of water they need to thrive.
It's Great If You Travel
Self-watering containers are also the perfect solution if you travel and can't keep up with the watering needs of your plants. They also work well if you have a place where you want a container, but its location makes it awkward or difficult to water. We have found that the harder a container is to water, the less likely we are to do it. We have killed many plants by forgetting to water them or dodging the chore because it is difficult or inconvenient.
Work on a Reservoir System
Self-watering containers work on a reservoir system. There is a water storage tank, usually at the bottom of the container, which you fill. There is an overflow hole, so excess water simply drains away. The soil soaks up the water from the bottom, so as long as you keep the reservoir filled, your plants get a consistent level of moisture, delivered directly to their roots.
The reservoir system makes self-watering containers very water efficient. Because the water is stored out of the sun and wind it evaporates more slowly and there is less water loss than if you spray water on your plants. There is also less chance of fungus and disease because you keep water off your plants' leaves by feeding them directly through their roots.
The Many Types of Self-Watering Containers
There are many types of self-watering containers, from decorative to purely utilitarian. Those that are more utilitarian, are specifically designed for vegetable container gardening and to maximize yields. The generic name often used to describe utilitarian self-watering containers is grow box. There are several brands of grow boxes (one even called "Grow Box" and lots of instructions on the web for how to make your own.
The Brand to Buy
Our favorite brand of grow box is the Earthbox. In fact, it is our absolute favorite way to grow vegetables, especially tomatoes. We have had incredible yields from Earthboxes and our plants have grown to outrageous heights and have been lush and gorgeous. A huge advantage of the Earthbox system is that even if there is too much rain, the plants are protected from sitting in soggy soil because the soil is covered by a plastic cover--that kind of looks like a giant black shower cap. If there is too little rain, you completely control the amount of moisture by adding water to the reservoir. Also, you add fertilizer at the beginning of the season, when you plant your box and don't add it again for the entire summer.
We have also had great success with The Organic Tomato Success Kit from Gardener's Supply. We have tried the Grow Box system which worked well but did not come in an organic version and had a huge logo printed on the soil cover, which We didn't like. I'm not crazy about providing advertising space in our gardens.
Our favorite decorative self-watering containers are made by a German company called Lechuza. Their self-watering container gardens are sleek, modern and come in fabulous colors. They have a unique irrigation system that works beautifully both indoors and out. These planters are pricey but are gorgeous and have the quality to match the price.
On a smaller scale, we have discovered that the only way we can successfully grow seeds is to use self-watering containers. We love the system APS System from Gardeners Supply, but we wanted to figure out an less expensive system that schools and community centers could use to start seeds successfully. We came up with a design where we used a supermarket plastic pie holder and cotton string to wick water into the soil. We're happy to say that the system works really well. The string wicks water up from the reservoir and keeps an even moisture level while seeds are germinating and then after they sprout.
Mike Lieberman, who runs the website Urban Organic Gardener, has instructions for making your own self-watering container out of recycled 5-gallon buckets.
There are some plants that you shouldn't put into self-watering containers. Succulents and cacti and any plants that like to thoroughly dry out between watering. It is said that many herbs won't taste as strong if they are kept in damp soil, and some, like rosemary, prefer to dry out between watering, but honestly, We can't tell the difference. Also, herbs and some flowers, like nasturtiums do better if they aren't in a rich and highly fertilized soil, so research your plants' requirements before putting them in self-watering containers.