Plants need carbon dioxide, water, light

Whales can be 50ft in length, weigh 20 tons, and have a appetite to match. A fully grown Saman tree such as one might see in the grounds of the University of the West Indies in Trinidad will have the same dimension, and the same appetite. Whales consume krill and other small forms of marine life in vast quantities and breathe out vast quantities of carbon dioxide.   Trees (and all plants containing chlorophyll) consume vast quantities of carbon dioxide and give off oxygen.

All forms of animal life require oxygen to survive and all forms of plant life require carbon dioxide to survive. Plants and animals complement each other and are totally dependent on each other.

Most successful gardeners now have an instinctive knowledge of the fundamental facts which make for being a successful gardener. If they did not they would not be successful gardeners.

The essentials (as well as the need of plants for carbon dioxide) are water availability, and light.   They also need to have a knowledge of the natural areas from which their plants come in their never ending quest for perfection.

Commercial growers in Europe and North America pay particular attention to these essentials for successful plant growth as their living depends on it, and especially when important crops are grown in glasshouses. Nowadays vast quantities are grown in enclosed areas and their requirements have to be calculated very precisely. In the past I visited large-scale growing units where growing is done all the year round under systems which might be described as fully automated. There carbon dioxide, water, and light requirements are fully automatic which at times seems beyond belief.

A glasshouse full of thousands of plants of tomato can easily run short of any of the essential ingredients, and the shortage of any one of them can bring growth to a dead stop. The only way to get it started again is to supply the ingredient which is in short supply, so if the carbon dioxide content is insufficient to allow full growth, then the modern glasshouse manager just turns on a tap to pump carbon dioxide gas into the air.

If growth is rapid water may become short. This is measured by soil tensiometers placed in the ground throughout the glasshouse. When they indicate that water is in short supply the manager just has to turn on a tap to get water into the ground. If water is in short supply then growth will stop at once, no matter how plentiful the supply of carbon dioxide and good light.

The same thing applies to available light. If light is limiting growth, all that’s needed is for a switch to be turned on. And of course the most important point always to bear in mind is that during the process of using carbon dioxide plants give us the oxygen we need for our survival.

The Amazon rain forest alone consumes billions of tons of carbon dioxide and in return gives us billions of tons of oxygen. For the ‘ordinary’ gardener extreme conditions such as might occur in a glasshouse when used for intensive cultivation might not occur. They might occur in a propagating case which is massively overcrowded with cuttings, especially when you might forget to put a crack of air on in the mornings or forget to supply them with water or remove the shading. Shortages like this are not likely to occur in our typical shade shelter when there is bound to be a free exchange of air.

Until next week may your God go with you wherever you may be.

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