They really do grow fast!
Guess, since they come from a desert area, they have to grow fast in order to survive arid conditions! The seeds germinate during the rainy season and have to grow and swell to store moisture to get them through the rainless seasons!
One piece of advise I go by with any plant species is, "research, and gather as much info on any particular species, then try to duplicate the proper germination and growing conditions"....In other words "know the plant and its behaviour"
Adenium really are cool fun tropicals!
But, they still come second to the cacti species I'm growing!
The winter hardy ones I'm growing are slow, and somewhat finicky as to the amount of moisture and sun to give them until they are older and better able to tolerate the extreme growing conditions they will have to survive out in my sandy, hot, dry gardens! One essential requirement is that they have to have well drained soil conditions especially during the late Fall, Winter and early Spring!<---and that is exactly what I have for!
Green fingers, and green toes!