Here is an article about clivias here. Clivias (with the exception of a single newly discovered species) are native to eastern parts of South Africa where the rainfall comes mostly during the summer (the opposite of our conditions). Haemanthus are native to exposed locations in the Western Cape but are dormant during the summer drought when light intensities and temperatures are at their highest.

Clivias can also be found on the margins of woodlands settings where there are openings to rivers/gorges, etc which will be less dark than closed canopy forests. Not all Haemanthus come from the winter rainfall areas, several species can also be found in the eastern cape with year round rainfall and on into Kwazulu-Natal, where it is summer rainfall or spring/fall. There are species of Haemanthus which occur along the coast in dense evergreen thicket type vegetation, in summer wet grasslands up in the mountains, and into the northern interior of the country which is hot and wet in summer and cold and dry in winter. The western cape species come from regions with climate and rainfall more similar to southern California, and are more often found growing in full sun. These would include H. sanguineus, H. pubescens, and H. coccineus.

The summer rainfall species of Haemanthus can be found growing in actual forests, they also can occur in subtropical shrub-thicket type vegetation, and higher elevation mountain grasslands.

A couple of good books which might help you with answering such habitat questions is by author Elsa Pooley, A Field Guide to Wild Flowers Kwazulu-Natal and the Eastern Region, and/or South African Wild Flower Guide 7/West Coast, by John Manning and Peter Goldblatt.