What do you need to ensure that big plants can be used successfully in an interior landscape?

Large plants are frequently used as the main focal point of an interior landscape, either as solitary specimens or in formal groups, such as an avenue of trees in an atrium or shopping centre. For the purposes of this part of the module, we are talking about plants more than 2.5 metres (8 feet) tall or with a spread in excess of 1.5 metres (4 feet).  These tend to be large trees that can be very expensive and difficult to source, so it is worth getting it right.

Such big plants are very different from smaller specimens in that they have special requirements for installation, watering, cleaning and pruning.  Some of these items are covered in greater detail in Module 4: Health, safety and the environment and Module 5: Installation and maintenance of plant displays.

Stability and anchorage

Large trees weigh a lot and they can be top heavy.  Often, they are supplied in surprisingly small nursery containers. This means that the plant's roots are a little constrained.  Before the plants are put into their bed or tree pit, it is important to tease out some of the roots to encourage them to grow into the fresh soil.  This will provide extra anchorage and give the tree better access to water and nutrients in the soil.

The soil mixture used for large trees is often different from that used for smaller plants.  It often has a high loam content (instead of peat or other lightweight material), which is much denser.  This provides much greater physical stability to the tree.  Be aware, however, that as loam-based soil mixes have a much greater density than lightweight mixtures, the overall mass of the plant display will be considerable.   A loam-based medium can have a bulk density as much as 10 X that of a peat mixture, possibly as high as 1 tonne / m³  (1,686 lb / yd³).