I have a special affection for this plant, since it was the main subject of my doctoral thesis work on micropropagation of geophytic pelargonium species. Basically I developed a protocol to grow new plants from leaf sections, since P. luridum cannot be propagated from stem cuttings as there is very little stem to begin with. I also made some really cool hybrids with it that required a modified embryo rescue technique to bring into existance. I no longer have those hybrids, but I did distribute them so hopefully someone has some of them, such as the hybrids I made with P. incrassatum, sericifolium, and cortusifolium, among others. P. luridum can also be propped by dividing the tuberous roots, which resemble small potatoes on a string. It is a summer growing plant, with large divided foliage (foliage gets more divided as daylength increases) and cream, pink, or yellow flowers in the forms I have grown. A closely related species, P. zeyheri, is essentially identical except for its very finely divided foliage, so fine that it resembles fennel--it is a gorgeous foliage plant.
P. luridum is winter hardy in protected locations, if the tuberous roots are planted deep enough. I keep some inside for the winter too, just in case something were to happen to the outdoor plants. It does not set seed readily unless another clone is around, and prefers a sunny place to flower well. The flower stalks are pretty tall so they will flop unless supported in some way.
My most treasured form is a yellow flowered form from Malawi, which I keep in a large pot and would not think of putting outside. It is much more reticent to flower, and when it chooses to it does so before the foliage emerges, unlike the South African forms which will flower continuously during the summer if they have enough sun.