Having a grayish-blue or whitish appearance, or the quality of becoming glaucous with age or development.
From Latin 'glaucus' (bluish-gray) plus the suffix '-escent' meaning 'beginning to be' or 'tending toward.' This creates an adjective describing things that have or are developing a grayish-blue tone.
The '-escent' ending is like saying 'kind of becoming'—glaucescent leaves aren't fully gray, they're in that in-between state, which is exactly what many plant species show as a defense mechanism that develops with maturity.
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