And bearing in mind that there are only four SA species listed, I’ve added tags to all my Wachendorfia observations to make it easier to compare them.
The very tall and spectacular one, in my opinion, is
The others are (with my notes attached)
Wachendorfia brachyandra 20-65cm
Leaves hairless.and usually shorter than the stem;
Stamens & style HALF as long as the tepals;
Wachendorfia multiflora 10-30cm
is quite easy if one checks the bracts - the only ones that are green;
Leaves are narrow and softly hairy,
Wachendorfia paniculata 20-70cm.
Leaves narrow and usually hairy, pleated;
Flowers in panicles (a branched raceme);
Habit mainly sandstone soils.
The tall one Wachendorfia thyrsiflora
Leaves are generally broad and glabrous.
Flowers in a crowded, cylindrical panicle, golden-yellow,
Habit permanent marshes and streams.
Just a reminder: all the flowers are enantiostylous, so if comparing look out for the alignment of the style on the different plants.
Another reminder: I may not always have the correct ID so please feel free to comment.