During the past fifty years there has been a quiet revolution in the commercial production of pot plants. Nearly every task has been automated, as commercial growers, needing to make a crust in the face of increasing labour shortages and consequent high labour costs, have converted nurseries into highly efficient plant factories. This has meant savings for the commercial grower, and headaches for the private gardener who has had to make serious adjustments to the way they maintain their pot plants.

John Warrington

In the old days commercial growers had to crank open the ventilators of their glasshouses by hand. Not any more. Your modern nursery ventilators open or close automatically in response to the temperature inside.  Carbon dioxide, absolutely essential to the growth of plants in daylight, can often be in short supply in a glasshouse in which there are hundreds of thousands of plants. Now growers can have it on tap and it can be introduced into the glasshouse atmosphere automatically once the sensors detect any shortfall in the carbon dioxide levels. Light levels are also now controlled just as carefully (and automatically), as is the quantity of fertilizer plants receive through the automated watering systems.

Generations of gardeners have known of the benefits of watering plants (especially newly sown seeds) by standing containers in water to allow it to rise up through the soil by capillary attraction. It was only just a matter of designing a system to do it automatically.  Conventional  glasshouse benches are converted simply by placing about an inch of sand over a spaghetti-type arrangement of perforated plastic pipes through which the water is supplied to the bench. The water supply is controlled by a simple ball valve such as one finds in a toilet.

Clay pots are too thick to make proper contact with the sand base, but plastics are just right. Conventional potting composts are too open and well drained and so soil-less composts were invented, which are fine enough to allow the water to move up. Now small-scale automatic watering systems for the private gardener can be bought to look after the pot plant collection, whilst the family can go and holiday on the Costa Del Nasty, the West Coast of Barbados or the Hindu Kush for a couple of weeks.

Like it or not, most of the problems we gardeners have to face are a direct result of the plants growing under automatic watering conditions and in soil-less compost. The reader will have guessed by now that I have for a long time preferred composts which contain soil, and pots which are made from clay rather than plastic. My view is that all plants can be grown better in clay pots than in plastic pots. Root development is better because of their porosity, and because they do not remain wet for too long. There is nothing quite like a clay pot.

The modern family has a lot of mobility. Mums and Dads go out to work, most do not have automatic watering systems and so those that grow in clay pots should have a peep at their plants morning and afternoon to make sure they have enough water to last the day, and are not gasping for water at the end of it. It helps enormously to protect them from direct sun and draughts.

It is my view that plants grown in clay pots do better in the old time potting mixtures based on 7 parts of loam, 3 parts of peat/fibre/compost and 1 part of sand.  It is open enough to allow perfect drainage – and don’t forget to place a crock in the base of the pot. If you’re anything like me you’ll always have a few broken pieces for that.

It is always understood that when small roots start appearing from the base of the pot it is time to pot on into a larger one. Plants grown in clay pots are perfectly happy standing on a gravel or cinders base which can be kept wet (but not flooded) to provide a little humidity and buoyancy.

Having said all that in praise of the clay pot, it is clear that plastic is here to stay and that I am fighting a rearguard action (but not a losing battle). We just have to learn to maintain the gifts we get which are in plastics, but must remember that with plastics the most common cause of death is drowning. The motto has to be just give a little bit of water when you think they need it. Alter-natively you do what I do and re-pot them into a clay pot using traditional potting compost.
Until next week may your God go with you wherever you may be.