In my experience, Myrrh (which I don't believe is a South African native, more North Africa, Arabia...) can be quite touchy. In nature, it grows in rocky soils in the desert, so while young, it likes bright light and never to be overwatered. That being said, my seedlings died after 6 months. I am in a very foggy and mild climate here and you may have more luck in Texas...
Dan

How did your myrrh seedlings turn out? Do you have any extra seeds to sell?I I could not find them listed at silverhills seeds. thanks

I went to the Silverhills Seed page and selected catalogue and then entered just the word Myrrh. It came up with 2 mathches. The seeds are 3.00 per pack. I didn't check about the shipping though.
Stevi K

Hi, I grow various pachycaul trees, caudiciforms, etc. as both a hobby and small business. I particularly like the Burseracae family, as it has many nice gnarly little trees that work for bonsai. There are many species of Commiphora which grow in Africa, Madagascar and a few other areas. There is a specific species that is Commiphora myrrh that I believe is from North Africa and Arabia, not South Africa. The species you got is probably one of the many from southern Africa. Although some come from areas where there is some frost, most do not do well in freezing or low light conditions. Bright florescent lighting is probably OK during the winter. I have pictures of a few Commiphoras on my Webshots link below.

Here is a link that might be useful: Pachycaul & caudiciform pics