CULTIVATION OF BIG PLANTS IN CONTAINERS
As an increasing assortment of plants is being grown in containers, there will also arise a growing demand for bigger container plants which can be delivered all the year round. The landscape gardener, who has to finish his production in order to deliver it and get his profit home, may plant Pyracantha and Lonicera for ground cover, but if he is unable to grow (get hold of) the Planes or Robinia plants he needs for solitary planting, well, then he is back again where he started.
One of the principal reasons for container growing must be to supply the consumer with plants at all seasons. I am, however, not one of those people who firmly believe that all future plant production is going to take place in containers, it would certainly be an expensive affair to produce Ligustrum for hedges in that way. But there is quite a lot of plants with so fragile (difficult) a root system that they are badly damaged if transplanting takes place during their dormancy period, f.i. such plants as Betula, Larix, Robinia, Pinus austria, Pinus silvestris etc. These plants ought always to be container grown in order to obtain a far better quality, as you know this is also the case with smaller plants. I think much more stress should be laid on spreading information by means of radio, television and the press to make the consumer aware of the importance of container growing and root quality. I find that even professional people, f.i. landscape gardeners worry far too little about root quality.
What is meant by big plants? By big container plants I understand that the containers must have a capacity of at least 5 litres. In the following I will mention containers with a capacity of about 100 litres.
The smaller containers with a capacity of 5–15 litres are made of plastic. Furthermore we have the concrete containers which hold 30–50 litres. The largest one we have, has a capacity of about 100 litres, it consists of a galvanized iron plate which is bowed (bent) all the way round so as to form a container without bottom.
To grow big plants in containers is very different from growing smaller ones, other problems as to watering, staking, transport etc. arise.
The application of sprinklers, nozzles etc. to big container plants will, owing to larger space between the plants, result in too much loss of water. Drip watering should here be applied, by means of this system the plants will in the best possible way receive the needed quantity of water and nutrients.
In Denmark we are so fortunate to have the Volmatic Watering System,