Good blooming David.
In all the years that I’ve grown warneri, they have shown characteristics that differentiate from its sister species labiata. These characteristics are pointed out nicely by both David and Geoff. These are summarized well in the Chadwick book.
I wanted to share my observations and have noted these patterns:
1. warneris start their new growths in Oct/Nov (as late as Feb/March) and mature growths in 3-4 months under ideal conditions. Good watering and fertilizer is needed for good strong growths. (versus labiata start new growths in spring around April/May and mature by August/Sept).
2. Ideal conditions are warmer night temperatures (15-18C) and bright light (2200-3000 fc). Any different will slow down the growths and may not sheath or bloom. They are not light period sensitive like labiata and requires 12 hours of light for health (they are from equatorial regions).
3. They bloom as soon as growths mature in summer, with as many as 3-5 huge 15-18 cm flowers that develop very fast. Best to groom flowers for best presentation as they tend to crowd. The stalk usually is strong enough to support without staking. Flowers lasts up to 3 weeks (4 weeks if kept cooler). Chadwick warns to keep buds in sheaths from burning if plant is close to window. (versus labiata which blooms after 1-2 months of rest after summer maturation, with two to three 13-15 cm flowers in fall). Warneri flowers are so big that the petals have a slight droop midway out, almost like mossiae, but less. The petals usually do not overlap the sepals (some select cultivars do but very rare) and windows are seen between sepals and petals. An ideal flower reduces this window with upright petals.
4. After blooming, the warneri starts rooting. (vs labiata that roots right away).
5. Warneri leaves are very wide up to 8 cm in some (vs 4 cm in labiata) making them appear short and stout. The leave color is also darker moss green versus labiata lighter apple green usually.
These are my observations that can help me tell the difference between warneri and labiata.
Caveat: as mentioned, imported plants may take 1-2 years to get on schedule.