I have read many post from newbies regarding how fast does a sulcata grow? They are trying to get an idea of what to expect. Well all I can do is show you how my Darwin has grown in just under 4 months. I do not clam to be an expert or anything, in fact I am still a Newbie myself. From what I read, they can grow at different rates. Some fast and some slow. I put these two photos together and zoomed in on the one to make my fingers the same size so you can see the difference in his growth in almost 4 months.