Self-watering Equipment

If you go away often, have lots of house plants, or just have trouble remembering to water them, a self-watering system is what you need.

The idea of self-watering is simple. Water is placed in a special ‘reservoir’ touching, or connected toself-watering-equipment, the potting mixture of a house plant. The water is then slowly absorbed into the potting mixture as it dries out, or is taken up directly by the roots. Self-watering equipment can be completely hidden. When it is visible, it may be either decorative or practical looking. And by adding fertilizer to the water, you enable the plants to become self-feeding as well! Plastic self-watering containers come in many attractive colours, and can be square, rectangular or round. (Unless you look closely, they look like ordinary, decorative pots.) Especially useful are self-watering hanging baskets and wall pots.

Sizes vary from small pots to huge planters for offices. The reservoir is either part of the container or forms the lower half of a two-part container. You fill the reservoir through a special opening in the side or through a tube at the top. More expensive models have a built-in water gauge.

How they work

The containers operate in different ways, but all come with easy-to-follow instructions. One type has perforations through the base, like the drainage holes of a flower pot, and a clip-on, tight-fitting reservoir beneath. With this type you place a layer of gravel in the bottom of the container to prevent the potting mixture falling through or clogging the holes, then plant up as usual.

At first, you water from the top, and excess water drains into the reservoir.

Once the roots grow through the perforations – it is easy to check this by carefully unsnapping the bottom half of the container— water directly into the reservoir, through the hole provided. In this way, the tips of the roots are kept in contact with the water.

Another type has a water-absorbent fabric band stretched across the bottom, so that half the band is in the reservoir, and the other half touches the potting mixture. As the mixture dries out, water is absorbed from the fabric band, which acts like a wick, drawing a fresh supply from the reservoir.

Some containers have a narrow, vertical tube of potting mixture which you keep fully saturated. This moist compost acts as a central wick, slowly releasing water into the remaining potting mixture surrounding it.

Capillary mattingcapillary-matting

This is a spongy, absorbent plastic fabric, which can be cut to any size. You place one end of it in water, perhaps in a sink, then place uncrocked, plastic plant pots on the other end (on the draining board). Water is drawn up along the whole matting, then up through the drainage holes into the potting mixture.

Small reservoirs

The simplest small reservoirs are unglazed clay ‘bottles’, which you sink up to their rims in the potting mixture and fill with water. Water is slowly drawn through the sides into the surrounding potting mixture.

  • There are special plastic cups with tiny perforations to fit into the tops of moss poles. The pot is filled with water, which is then slowly released at the same rate as the moss dries out.
  • Insert glazed clay ‘frogs’ into the compost, so the porous reservoir is buried. Fill with water.
  • Remove enough moss to insert the water cup flush with top of mesh. Fill with water; re-fill as needed.

Hollow tubes

These work very well, and are popular in greenhouses and with professional growers. With house plants, one end of a tube is placed in a water supply and the other is connected to a water-filled clay cone pushed into the potting mixture. The water is gradually released from the tube into the potting mixture, and this sucks more water from the reservoir into the tube. Larger pots, 25-30cm (10-12 inches) across, need two cones, opposite each other. Long containers, such as window-boxes, need cones every 20-30cm (8-10 inches).

  • The tubes can detract from the overall display, so many people prefer to use them only when going on holiday. Absorbent fabric wicks can be improvised to be used in the same way.
  • Fill the clay cone up to the brim with water, then close it tightly. Insert the porous clay cone deeply into the potting mixture. For large pots use two cones.
  • Lower the feed tube into the reservoir so the end reaches the bottom.


What is meant by ‘capillary action’?

Self-watering systems depend on capillary action, which is water’s ability to move upwards against gravity, through finely divided or porous particles, such as potting mixture.

The see-through bottom of my self-watering container has gone green and smelly. What should I do?

Any standing water, especially in transparent containers, can develop algae. Scrub out the container regularly, using soap and warm water, otherwise the algae can block up the system.

Can I convert an ordinary wall-hung plant pot to a self-watering one so that it still looks attractive?

Yes. Fix an ornamental water receptacle, such as a decorative vase or jug, to the wall or rest it on a table underneath. Insert a water-filled clay cone into the compost, then run the tube to the reservoir. If you grow trailing plants, they will hide the tubing.

How often do I top up a self-watering system?

This depends on the size of the reservoir. As a general guide, self-watering containers need refilling every 3-4 weeks, and small reservoirs every 2-3 weeks.

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