To monitor the rate of leaf unfolding, flag 5 to 6 average plants in the greenhouse. With a pen or a hole punch, mark the last unfolded leaf, then count the number of leaves unfolded on the same plant. Record this number. Marking the last unfolded leaf each time makes counting easier. Do not disturb the plants any more than necessary.
Mechanical stress reduces growth, and can foul up graphical tracks.
Dividing the number of newly unfolded leaves by the number of days gives the daily rate of leaf unfolding since the last count. If the unfolding rate is greater than the required rate, then greenhouse temperatures may be lowered slightly, and vice-versa. It's critical that leaf counting and temperature manipulation must begin immediately after flower initiation has started. Small temperature increases over a long time period are very effective in increasing the rate of lily development, but short pulses of high temperature are nearly useless and probably detrimental to quality.