Pots need to be chosen with a view to the quality of the cyclamen plant as well as their looks, and the consumers’ taste.
The choice will depend on the type of watering system and the properties of the growing medium.
For terracotta pots, those that have been treated against moss are better; in the case of plastic ones, they should have plenty of holes at the bottom and studs to raise them from the surface.
A study was conducted in 1991 by the CNIH (The French National Committee of the Horticultural and Nurserymens’ Industry) to establish the importance of the choice of pot (plastic and terracotta pots). The object was not to show one material superior to the other, but for each material to determine which ones in the range were the most suitable. In the case of trough streaming irrigation the important effect of pot design on successful growing was demonstrated, and it was possible to show which models were suitable for the technique of irrigation from underneath.
First, various commercial brands of plastic pot were tested. The models chosen all had roughly the same volume for a given diameter (12 to 13.5cm): the main differences were among the pot bottoms (number, size and shape of holes, and whether or not the pot had any projection to raise it from the surface). In order to establish the impact of the various pots, the following variables were measured:
As a result of this study it is clear that the choice of pot has a very definite effect on the weight of the plant and the density of foliage. The height and diameter, on the other hand, and the number of buds, showed no significant difference among the types of pot.
It emerged from these trials that in the case of cyclamen the pot volume and the technical characteristics of the pot bottom had a fundamental importance for successful growing. What must in fact be considered is the amount of contact surface between the medium in the pot and the external environment (air or water). A good balance needs to be found so that there can be the best possible contact between compost and air, without forgetting the water too.
The study concluded that the best were 6-holed pots (for 13-14 cm) with a very small projection (2 to 3mm), enough to allow the stream of water to pass, while still providing for a good contact with the growing medium.
Secondly, the study examined the influence of the shape of the various terracotta pots on water supply, and hence on plant growth. The technique of irrigation from beneath studied was still that of trough streaming.
The models chosen all had roughly the same volume for a given diameter (13 to 14cm). The main differences among them concerned the bottoms (4 or 5 holes, their size & shape, projections or not).
In order to establish the impact of the various pots, the following variables were evaluated:
In the case of cyclamen there were very distinct differences among the pots, including the total flowering potential. The extent of algal and moss disfigurement also varied.
The study concluded that the shape and the kind of bottom made even more difference for terracotta pots than for plastic ones, under the trough irrigation system. Here again, the surface in contact with the air or water would seem to be the most important variable. In the case of terracotta, the quality of the moulding is also a fundamental factor. What the pot needs is slight projections, raising it by a few millimetres, accurately and cleanly executed. It is harder to do this because the pots are more fragile.
The advice of the CNIH, then, when it comes to the trough irrigation system, is to choose a model which is slightly raised off the surface, by 2 or 3mm, very well finished, with 5 holes as large as possible. The terracotta pots are harder to manage in irrigation systems since watering takes longer (the holes are smaller and fewer, and water is absorbed by the pot wall).
Anti-algal treatment, which avoids the need for cleaning the pots, has no effect on plant growth.
Terracotta pots have the advantage over plastic ones that their walls are permeable to air and water. They have the disadvantage on the other hand of allowing algae to grow on their outsides in summer so that they have to be cleaned for re-use.
Terracotta is also heavier than plastic, which means an extra burden on the staging and for maintenance and transport.
However that may be, it is clear that we must use pots which ensure that the roots have good contact with the water and air. Our choice then will be of pots with enough holes, without neglecting the question of their commercial value when it comes to marketing the plants.
The degree of raising of the pots should in every case be adapted to the type of irrigation: it must depend on the level of the water surface.
MOREL P., GRANGER J.- Comparaison de poteries plastique en subirrigation. Les cahiers du C.N.I.H., Février 1991
MOREL P., GRANGER J.- Comparaison de poteries en terre en subirrigation sur cyclamen. Les cahiers du C.N.I.H., Mai 1991
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