I have just received 6 concinnum bulbs and 6 speciosum bulbs. I would like to plant these in a small area in front of a large tree. I would like to design it so that one species is behind the other. Which species would you place to the front? I was thinking ideally I would like the larger one to be behind, but there are varying reports about height, etc. Certainly, the speciosum 'looks' fuller, so perhaps it would be the better one to be behind?