My garden has to work extra hard. It is for all my clients but also it is for me and my family.
I want to be able to test plant combinations and experiment with what works and what does not, but at the same time, it is a small, north-facing garden in London, not an expanse of rolling landscape hidden deep within the countryside. Ah sigh...
In a small London garden, space is premium. Each plant has to work hard to justify its place.
A large percentage of evergreen is used to maintain all year interest. Focus is on texture and colour of foliage, not necessarily on flowers (but they do of course make an appearance).
There is no place to hide for a plant that's not having a great day.