booting stage BO.01 early boot stage 5.01-flag leaf sheath extending in barley (related) PO:0007018 5.1-early booting stage in rice (related) GRO:0007091 flag leaf sheath extending (related) plant_structure_development_stage 5.01-flag leaf sheath extending in oat (related) 5.01-flag leaf sheath extending in wheat (related) The flag leaf sheath has started to extend. GRO:0007149 rice growth stage-5.1 (related) In rice the flag leaf sheath is 5cm out of the penultimate leaf sheath. Upper part of the stem is slightly thickened. Booting is a term used specifically for grasses (Poaceae).