AOS and unflowered plants
As per AOS rules, plants awarded a CBR or CHM (the awards typically given for foliage plants) must have flowers. Unflowered plants may only receive a JC (see Stenosarcos Vanguard 'Fireball' JC/AOS). The reasoning behind this is that CHM and CBR descriptions are the AOS equivalent of a "type" description and set the precendent for the species for years to come; this precendent must include flowers, so that the species could in the future have a rubric with which to compare for flower awards. Occasionally, plants exhibited for foliage win JCs, which are then changed to CHMs upon re-exhibition with flowers. Another major difference is in how JCs and CHMs are voted upon - a JC takes 75% of judges giving a "yes" vote for the plant to get the award, which has no point value, while a CHM is a typical point-scored award, with higher points being awarded to species of high "horticultural merit" (the "HM" part of the CHM) like Phrag. kovachii, awarded a 94 (? I think) point CHM on its first exhibition.
This is all much more complex for hybrids, for which CHMs and CBRs may not be awarded.
Hope this helps....for more info refer to the AOS handbook on judging and exhibition, probably available from your local society's library.
-Tim