Carmen showy sedum is a cultivar of the large-flowered, herbaceous, perennial sedums that comes closest to a true red flower color. Growing 18 by 18 inches, this fall-blooming perennial thrives in average soils with average water. The blooms are a butterfly magnet. Hylotelephium used to be called sedum until the DNA was analyzed. Both genera remain members of the Crassulaceae, which were the first group of plants discovered with the Crassulean Acid Metabolism (CAM) approach to photosynthesis. For those not familiar with the process, water (H2O) plus carbon dioxide (CO2) in the presence of light within a chloroplast (containing enzymes) produces sugars (multiples of CH2O) used to supply energy for plant cells. In CAM plants, some of the chemical processes are delayed until the sun goes down, and the danger of transpiring (equivalent to perspiring and breathing combined in people) is less likely to result in the loss of large quantities of water.