To put forth or develop fronds or leaves; to become leafy or to begin producing leaf growth.
From Latin 'frondescere' (to put forth leaves), derived from 'fronda' (leaf/frond). The verb developed in botanical and scientific contexts to describe the natural process of plants leafing out.
This verb is almost never used in modern English, but it perfectly shows how Latin could generate whole families of words—you have the noun (frond), the verb (frondesce), and all their variations describing the same natural process.
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