I think it is not safe to generalize, but I was most amazed to see how much of the Cape area had acidic soils, with only occasional outcrops of limestone soils/rock. Especially the sand based soils were mostly acidic, and especially so in the higher mountain areas, as well as right along the coast. Even the water in creeks and rivers was often quite acidic.

It would be safer to look up the typical habitat for the bulbs you are growing and decide ph based on this... Our soils and water here in the Sf Bay Area is mostly neutral, and I find that I have the most trouble growing mediterranean plants,(not necessarily all South African) that prefer limestone soils, they just fail to thrive for me. It has been frustrating trying several wonderful plants from seed collected in Crete(mostly all limestone or basic ph), perish in the second year, although our greater winter rainfall and heavy clay soils could also be the culprits.

Hi RJ,

I have never bothered with measuring ph, so I don't know whether my garden is acid or alkaline. Only just recently I have heard that the SA standard for potting mixes is between ph 5.5 and 6.5.
I am mainly growing succulents (all kinds, from all over the world, but obviously have more South African stuff), trying to get most of them out into the ground but not succeeding, so I have many in pots now as well. For these I have been using a mixture of commercial seedling soil and coarse river sand for years (at a ratio of about 2:1, but increasing the sand for more rot-prone species) for everything, all the succulents, bulbs and ground orchids - after all they all grow together in their habitat. I would only add acid compost or lime if it is specifically mentioned for a certain species. Half the time I don't know what I am growing anyway, or where it comes from. And if I do know where it comes from, I have no idea what the ph is in that paricular place....
When preparing a garden bed for succulents and bulbs specifically, I just add compost and river sand to the ordinary garden soil.
It seems to work well for all of them, and also for me, as I have far too many plants to make up individual mixes.
One thing I would routinely add to the mix though is bone meal - if I didn't have any dogs! Did it for the hanging baskets last year, and it worked wonders. But for anything positioned below 1,5 meters I had to learn the hard way that this is an absolute no-no if you have canines...

Maddy