Why do some plants need an "open" position?

Question

The guidance for some plants (eg, some Australian natives like banksias) says they need an "open and sunny position". The sunny part is self explanatory. But why do they need an open position in addition?

Answer 1

Some plants may be susceptible to root rots and perhaps fungal problems on the upper parts, and thus need good drainage and airflow around them; an open position, not closed in or crowded by other plants nearby, means these problems are less likely to occur. Banksia is one example of this type of plant.