Susan,
Go and have a look at the website of the SA National Botanical Institute and have a look at the various botanical gardens. I only know the Witwatersrand BG personally, which is, especially if you are also also into birds, well worth a visit. Kirstenbosch in Cape Town is a must!
Maddy

Here is a link that might be useful: SA National Botanical Institute

Lucky you! Get ready for a magical experience. By far the best place in all of South Africa for gardeners is the Cape Town area. First, it's where Kirstenbosch is located...one of the foremost botanical gardens in the world. But, best of all, is the area south of Cape Town, where you can take day trips to drive through the Fynbos ecosystem, a truly unique biome. The drive down the coast is magnificent and there are incredible species growing wild by the roadside...Proteas, Moraeas and many others. The national park at the Cape of Good Hope is spectacular for its diversity. And just a little further down the road (ask any local) you can find an amazing community of Jackass Penguins. Also, don't miss the drive up to the top of Table Mountain...it's Protea heaven. In addition to the Kirstenbosch web site (use your search engine), you should also check out the site for the ARC (South African Agricultural Research Council). They have several research centers that are doing innovative work on ornamental and endangered species. You might even be able to arrange visits to their research centers just outside of Cape Town and Pretoria. (I did and enjoyed every minute!)

I'll be traveling to South Africa in October and want to visit great gardens. I'll have a week and center in Cape Town to begin with. Any suggestions for gardens and transportation and lodgings and eateries? I'm especially interested in kitchen gardens and ornamentals, not much into trees.
Thanks!

Ooh, I'm green with envy. Of course, Kirstenbosch. I suggest you join the SA Botanical Society. It costs about $35 US. Then you get free entry to all their gardens all over the country(which you can read about on their site). You could feel free to email all the chapter secretaries (whose emails are also on the site) for suggestions. You'd probably get at least one issue of their quarterly journal before you go, which has lots of ads for B&Bs in the back, and is a beautiful mag. Also, in January, you get to pick 15 free packets of seeds from them!

Here is a link that might be useful: SA Botanical Society