The last two decades have seen rapid advances in the technology used to
produce pot plants. Glasshouses designed and orientated to give maximum
light transmission, fully automatic heating and ventilating systems,
carbon dioxide enrichment of the atmosphere, controlled photoperiods
using automatic blackouts and incandescent lamps which enable plants
such as chrysanthemum to be flowered at any time of the year, mist
propagation techniques, chemical growth regulators which control the
height of plants, automatic watering and feeding systems, etc.: these
are only some of the developments which have transformed pot plant
culture. There have also been many changes in the composts and systems
used to grow the plants. Mineral soils, which formed the basis of the
John Innes Composts, are now either too expensive or too difficult to
obtain in suitable quality and sufficient quantity. Consequently the
grower has been forced to seek other materials such as peat, perlite,
vermiculite, plastic foam, shredded bark, etc. New types of fertilisers,
new methods of heat sterilisation and new chemical sterilising agents
are also being used.
