The Collaborative International Dictionary of English v.0.48:
Sadden \Sad"den\, v. t. [imp. & p. p. Saddened; p. pr. & vb.
To make sad. Specifically:
(a) To render heavy or cohesive. [Obs.]
Marl is binding, and saddening of land is the great
prejudice it doth to clay lands. --Mortimer.
(b) To make dull- or sad-colored, as cloth.
(c) To make grave or serious; to make melancholy or
Her gloomy presence saddens all the scene. --Pope.