Growing Plants in Containers
It is more than 50 years since the commercial growing of plants in containers was revolutionised by the introduction of new pre-formed, affordable plastic pots. Today the range and variety of pots and pot grown stock is seemingly endless. Most plants sold in containers are planted in gardens in the traditional way but more and more people, especially those with limited garden space, are choosing to grow plants "above ground" on patios, in wall planters and of course inside their homes.
Without wishing to state the obvious, a plant in a container above ground will require to be given all its nutrients and water by its owner. Plants cared for correctly will thrive in these containers and will add not only to the aesthetics of the home but will help to create a healthier environment.
The tub or container used to pot into should have drainage holes in the bottom and be large enough to allow the roots to grow out into the planting medium. A rough guide to size of container required would be double the volume of the existing root-ball of the plant for each year that the plant will be in that container. For example planting a 2L root-ball in an 8L container would give it sufficient space to grow for 2 years. (2×2=4, 4×2=8). Careful and regular repotting and refreshing of the growing medium every one or two years can be beneficial for container plants. However, plants will tend to grow better if they are kept moderately potbound. When it is time to pot on, plants should be allowed to keep a dense and fibrous root system, rather than putting them in to a very large container. Plants repotted into oversized containers will direct much of their energy into growing more roots. This results in less energy being directed towards growing leaves and flowers.
The planting compost must be chosen carefully depending on the type of plant being grown. Some plants are acid loving and grow in soils with a pH level of 5 or even lower. Others are acid hating and require a pH in excess of 7. Compost must always have the ability to retain moisture but must have free air space. Plant roots require aerobic conditions to flourish and will quickly die if the compost becomes completely waterlogged. Root rot is most likely to happen when using an oversized pot in relation to the root ball.
Nutrients supplied to the plant must contain the 3 main elements required for normal growth; potassium, phosphorus and nitrogen. These are known as the macro-nutrients and are required for root and leaf growth, and for flowering. Just as important are the micro-nutrients, calcium, iodine and manganese, to name just three. Micro-nutrients are needed by all plants to photosynthesise and grow. Compound fertilisers containing all the necessary plant nutrients are readily available from garden centres under well known brand names. A fairly recent innovation is to provide these fertilisers in a slow release form. A coating is applied to the granules which "dissolves" over a period of time based on the ambient temperature. These can be used to supply the correct nutrients to a plant over a period of up to 2 years.
Water should be given to the plant "little and often". Over watering causes loss of air space and leads to leeching of nutrients, especially nitrogen. Water requirement will be dependent on a number of factors including, plant type, season and the stage of growth the plant is at. Flowering plants show a marked increase in water up-take in the weeks leading up to the flowering stage.
Although growing plants in containers generally requires more input and care from their owners, they provide great rewards to the enthusiasts and brighten up areas all around the home.