If you are looking for a solution to be able to leave your flower boxes alone for several days while on holiday without having to find someone to water them. Or if you sometimes forget to water the flowers or want to keep this work to a minimum, then planters with a built-in water reservoir could be of interest to you. I will now describe how these work and what advantages they offer.

Such self-sufficient planting systems are available not only in the form of plant boxes, but also as plant tubs and plant pots. Depending on the supplier, the exact way they work can vary slightly, but the basic structure is always the same:

  • An inner part in which the soil is located and the plants are planted
  • A surrounding outer part that serves as a water reservoir
  • And a connection between the inner part and the outer part that allows the plants to access the water

The main difference between the various products offered on the market lies in the last point, i.e. the way in which the plants use the water reservoir. Some manufacturers talk big about an integrated irrigation system, but basically the principles that are used here are quite simple and long-known:

Self-collection of water via the roots

With this system, the plant is initially watered in the conventional way from above until its roots grow further and further down into the conical bulges in the base plate. These so-called suction funnels are permeable to water, so that the soil in this area is moist and supplies the plants with water. Growth into this area is sometimes supported by a layer of substrate above the dividing floor.

If the roots have penetrated deep enough into the suction funnels, watering from above is stopped and instead the water reservoir is filled directly from now on, so that the plant can use it independently via its roots and needs to be watered less often.

Example of the structure of the system described above. Left with the lock inserted when used in the living area, right with the lock removed when used outdoors (water must be able to drain away when it rains above a certain level), image: LECHUZA

Since most plants don’t particularly like having their roots permanently in moist soil, such a system always includes phases in which the water container is left without water for a few days so that the roots can dry out. For this purpose, the fill level is shown with a water level indicator so that you can adjust your watering behavior accordingly. The pioneer of these systems is the company Lechuza. However, they also offer systems of the second type, described below, which work with a wick.

Systems with wick, cord or fleece

These systems are all based on the principle of capillary irrigation. This can be imagined as a sponge lying in water. Even if only the underside of the sponge comes into contact with the water, the entire sponge absorbs water. The water climbs from the bottom to the top as if by magic. Other examples are the wick in an oil lamp, blotting paper or diapers. Certain materials are therefore able to bring water from lower to higher levels through a natural “suction effect”.

In self-watering plant pots, cords, wicks, cords or fleece made of cotton or fiberglass are mainly used for this purpose. These hang from the planting area into the water reservoir, absorb water and ensure that the plants are continuously supplied with water.

Example of the structure of a system with wick, image: LECHUZA

Both systems are usually equipped with an overflow through which excess water can escape. This is especially important if the plant is outdoors, as otherwise it would become waterlogged during heavy rainfall. If the water level in the water reservoir exceeds a certain level, the excess water flows away. If the plant pot is in an indoor area protected from rain, you can close off this overflow, as you can then control the water level yourself.

How long does the water supply last?

There is no general answer to that. The answer depends on the size of the tank and also very much on the type of plants planted. And last but not least on the weather and the location of the plant (sunny or shady). Depending on that, the plant can survive for a few days to several weeks with a full tank.

What types of planters are available?

Self-watering containers are available in all possible shapes and sizes. From small flowerpots to large balcony boxes, round or square, narrow or wide, low or high, bulky or delicate. The products I know of are all made of plastic. The largest supplier is Lechuza, which has been active in this field for more than 20 years. Other alternatives include Pflanzwerk, Deuba, Kreher, Formizon, Vivanno or Ondis24.

What are the disadvantages of planters with water reservoirs?

First and foremost, they require more space than conventional products, as the reservoir logically makes the flower box larger.

And they are more expensive: Established brand products such as those from Lechuza cost noticeably more than normal planters. If you need a large number of them, it can be quite expensive. In such a case, it might be worth trying one of the numerous lesser-known competitor products, some of which are significantly cheaper. You can also find some DIY instructions online to build your own flower box with a water reservoir, usually based on the principle of capillary irrigation, i.e. with a cord or wick.

Another potential disadvantage is that you can only intervene in the system to a limited extent. If it works well, no problem, but if the plant gets too much or too little water, you can hardly influence this by manual intervention.

And young plants cannot be supplied with water in this way, as their roots are still too short. These must first be watered from above in the conventional way for a few days or weeks.

Cover photo: LECHUZA