This indicates that Whitebird requires more GDD for each leaf to develop than does Merit. Whitebird has 3 fully developed leaves and one tiller. The number of tillers that develop is dependent upon both genetic and environmental factors.
Some varieties are more free tillering than others.
Barley is generally more free tillering than wheat. Stresses resulting from inclement weather, too little or too much water in the soil, soil compaction, deep seeding, or nutrients out of balance may all cause decreased numbers of tillers to develop. Merit has 4 fully developed leaves and the 5 th is about 0.5 as long as leaf 4. Tiller leaves emerge from a sheath, called the prophyll, which can later be found enclosing the base of the tiller. The prophyll can be used to identify tiller leaves from those on the main stem or other tillers.