This photo was taken on 8 Feb 10, and thus far I have always seen them in bloom. Since they are closely related to the Pseuderanthemum, they should be very easily propagated and I shall plant some nearer the Visitor's Centre in the near future.
NB on 7 Dec 10: I think this plant is known as Ruttyruspolia 'Phyllis Van Heerden', an intergeneric hybrid between Ruttya ovata and Ruspolia hypocrateriformis. 2 links are shown here: