Can the word "greening" be used in the sense of "being green" or "turning green"?

Solution 1:

It’s somewhat uncommon to see green used this way, but it is done:

Along my back porch in the herb bed the chive plants were greening and would soon be thick enough to cut.

Incubus, 1999

This is the continuous, not a gerund.

Solution 2:

It's unusual to use 'green' as a verb. However, some dictionaries have used it as a verb.

Green (verb - used with or without object): to become or make green.

Green (verb - intransitive, transitive): to become or make green

Origin: Old English grēne (adjective), grēnian (verb), of Germanic origin; related to Dutch groen, German grün, also to grass and grow.

From Merriam Webster:

Green

(verb) greened; greening; greens Definition of green (Entry 3 of 6) transitive verb

1: to make green 2: REJUVENATE, REVITALIZE intransitive verb

Intransitive verb :to become green Origin by MW: before the 12th century, in the meaning defined at intransitive sense

You can use it as a verb but it's very rare.