It is very common in the older parts of Sydney - presumably owing to its popularity in times long gone.In these gardens,t is often grown as an informal hedge and is said to be very easily grown from cuttings. It is no longer popular and is rarely (if ever) stocked by nurseries.
My tubestock sleeping hibiscus
The curious flowers never quite 'open' - they look like hibiscus flowers in bud. They are produced copiously so the plant looks colorful anyway. It is a sprawling (and slightly untidy) shrub, so it benefits from regular trimming. I've seen it flower both in full sun and deep shade but I prefer it in full sun as it remains compact.
This is an example of an old fashioned plant that should be seen more. It is hardy, drought tolerant and flowers for 12 months of the year. It is suitable for warm-temperate to tropical areas.
I recall one TV presenter receiving a call from a concerned woman that her hibiscus never open it's flowers like the one next door did - only to be told that her plant was in fact sleeping hibiscus!