Hydroculture is the technique of growing plants without soil or compost – all the elements for growth being derived from a nutrient solution. The method has made a profound impact on the houseplant scene in recent years – and has gone a long way towards making the growing of houseplants foolproof. Plants grown by this system are more expensive than those grown in compost. and it may be too costly to grow all your houseplants by this method. But for a special specimen, the cost is well justified by strong, healthy plants that will thrive with the minimum of care. It is also a highly recommended method for anyone requiring a ’cv superb houseplants but without the time to devote to normal watering and feeding. And in offices, where plants may suffer from irregular attention, they are ideal. Modern hydroculture units are clean. neat, and trouble-free. Watering is required only infrequently and feeding only about twice a year. Although there are several variations. all the hydroculture units for home use are based on the same principle: an outer container to hold the nutrient solution: a special inner pot containing the plant: an aggregate (normally expanded clay granules) to anchor the plant and provide the right combination of capillary action and air space: and a suitably formulated fertilizer. A device for indicating water level may be built into the outer container itself or be contained in a tube inserted into the aggregate, which also serves as a topping-up tube. Containers are usually plastic, the size and shape depending on the supplier. though square and round profiles are naturally the most widely used. Because a hydroculture unit contains within it a reservoir and items such as a water level indicator, as well as the plant holder, it is inevitably a little larger than a conventional pot containing a plant of the same size. Against that is the fact that you have a very presentable container that needs no further disguise before taking its place in the home. As they all perform well, choice is almost purely a matter of taste.

The clay granules and water-level indicator of a hydroculture unit.

Aggregate plays a vital role, and the type normally used is a special grade of light expanded clay ‘pebbles’ similar to those used as an aggregate for concrete mixes in the building industry. These are about 12mm (4in) in diameter, with a dense outer skin but an inner core of a honeycomb structure. Apart from serving as an excellent anchor, these special clay pebbles have the important ability to absorb water. and this helps to set up a capillary action which keeps all the pebbles in the container moist.

Fertilizer technology has provided the major contribution to making hydroculture suitable for home use. Soil normally acts as a buffer against incorrect feeding. but there is little margin for error when all the plant food has to come from a nutrient solution alone. The real breakthrough has been the introduction of ion-exchange fertilizers, which release just the right amount of food over a long period.

The chemistry of an ion-exchange fertilizer is complex, but the chemicals are bonded to tiny plastic beads and both major plant foods and trace elements are exchanged for impurities in the water. such as calcium, chlorine and fluoride. This exchange goes on at a rate that suits the plants being grown.

The fertilizer comes as a ‘battery’, which is lilted into the base of a compatible pot. or as loose granules which are spread on the clay pebbles and washed in with a little water. The amount required depends on the size of the container, but if applied at the recommended rate will be sufficient for at least six months.


Plants grown by this system are notably trouble-free, a periodic check of the water level indicator being the only routine attention required.

Hydroculture plants have the same light, humidity and heat requirements (bearing in mind minimum root temperature) as plants grown conventionally. They will only thrive if provided with these basic requirements. They are also subject to the same pests and diseases as plants grown in compost. They can be treated with all the usual insecticides used on equivalent plants grown in soil – including systemic types.

Watering is simplicity itself, and removes one of the major causes of houseplant failures. A water level indicator indicates minimum and maximum water levels.

Wait two or three days before Idling again, to allow air to penetrate between the aggregate. Do not be tempted to keep topping up continually: the roots must have a chance to be aerated. Always use tap water- at room temperature. Rainwater and even soft tap water will not contain the right chemicals to trigger the ion-exchange process. If you have a soft water supply, a few drops of a liquid houseplant food should be sufficient to start the process (it will not need repeating).

It is important to use water at room temperature because the roots can easily become chilled with this method of growing. Chilled roots can be a major cause of failure with hydroculture. If the water temperature falls much below 15 deg C (59 deg F), the leaves may start to yellow and the whole plant deteriorate. With some plants the air temperature may not be so critical, but root temperature is important.

Potting-on will be required only infrequently, as plants grown by this method do not make such an intensive root system and is normally only necessary when the plant becomes out of proportion to the container. Buy a slightly larger container, and a further supply of aggregate, and a recharge of fertilizer. Wash the aggregate before use. and place a layer in the base of the container. Stand the pot on this, ensuring the rim is about 12mm (jin) below the top of the container: stand the filler tube in one corner and insert the water level indicator, then pack the aggregate round the tube and the pot until the unit has been tilled.

Converting plants

This is not a job for the beginner, but it can provide a lot of interest and much satisfaction for anyone with the inclination to try. Always start in late spring or early

summer, so that the plants have several months of warm weather ahead. Start by washing the roots free of all traces of soil, but do it carefully to avoid damaging them. This must be done thoroughly. Once the roots are clean, pot the plant carefully into a container with open slatted sides (you can buy these from a hydroponics supplier), damaging the roots as little as possible while packing the aggregate granules around them.

The planting pot can then be inserted into the outer container, as already described for potting-on. From then on two things are critical -warmth and humidity. Keep the plant as warm as possible, but shaded from direct sunlight, to reduce moisture loss by transpiration. To maintain high humidity, spray with a line mist at least twice a day, or cover with a polythene tent for about a month. During this time try to maintain a minimum temperature

of at least 21 deg C (70°). After about a month, possibly up to two. the transition from soil roots to water roots should have been completed.

Suitable plants

Not all plants are suitable, and if you intend to grow your own hydroculture plants, experimentation may be necessary. Ivies, for instance, are not usually successful, but practically all the Ar-aceae family are: fortunately this includes many excellent houseplants. such as philodendrons. scindapsus and aglaonemas.

You can be sure, however, that any plants sold in hydroculture containers will be suitable.

Perhaps surprisingly, some succulents, such as mother-in-law’s tongue (San-sevieria trifasciata ‘Laurentii’) do well, although il is essential to ensure an adequate ‘dry period’ before topping up with fresh water.

Sorry, comments are closed for this post.