Some succulents are monochromatic – they have just one main color (usually green), but may have a variety of shades of that color. When creating a monochromatic arrangement, it's great to use different shapes and textures to add more interest.
What's the deal with this little rhyme? It's actually a “formula” that's commonly used in the world of container arrangements–and it's probably one of the most widely suggested guidelines for designing an arrangement.