PEAT AS GROWING MEDIUM FOR PLANTS IN CONTAINERS
On the other hand, pure peat is very little used as a growing medium for pot-plants. Primarily this is due to the fact that in Finland there is no great demand for plants in containers, and in particular the demand for flowering potplants is very small compared with the demand for cut flowers. The latest statistics indicate, however, that the situation is changing. Flowering potplants are becoming more popular among the customers, and at the same time growers are getting more interested in the growing of potplants. No special gifts of prophesy are needed to predict that there will be a keen interest among growers in pure peat as growing medium for plants in containers, as they all are aware of the excellent results obtained with peatculture in the culture of cut flowers.
In spite of the small importance of potplants in Finnish horticulture we at the Horticultural Institute in the University of Helsinki have carried out experiments with pure peat for growing of plants in containers for the lastfive years. Our wish to investigate the possibilities of using peat in this sector of horticulture was not simply due to the fact that we should have predicted the increase in the growing of plants in containers, visible today. Rather was the use of peat in container trials a matter of experimental technique.
First we needed for our experiments a growing medium that was sterile without steaming or disinfection. In the second place, we needed a growing medium with a homogeneous structure and available unchanged year after year. Thirdly, we needed a material containing in itself the minimum of nutrients. In the fourth place and particularly for pot-plant trials it was important to have a material, able to store the maximum of nutrition, so that only a minimum of fertilization would be necessary during the growing season.
On the basis of theoretical scrutiny peat seemed to meet the requirements we had set forth for the growing medium and thus it was chosen for the purpose. In the following I shall give a brief report on the experiences we have had of peat as growing medium in the container tests.
Chrysanthemum has been the main test plant in our experiments, though certain other plants, for example poinsettia and bean plants have been used as well. The growth and development of plants in peat was compared with those in sand, which is generally used as growing medium, especially in fertilization experiments. Loam, the most common growing medium in the commercial culture of plants in containers, was also used.
At first we had no great success in these experiments. In the beginning the watering of peat caused great trouble. The peat in the pots had a tendancy to shrink - apparently owing to drying and decomposition - and a sap was formed inside the container edges with the result that the outermost and most active roots