sadden \sad"den\, v. t. imp.  p. p. saddened; p. pr.  vb.
   n. saddening.
   to make sad. specifically:
   a to render heavy or cohesive. obs.
       1913 webster

             marl is binding, and saddening of land is the great
             prejudice it doth to clay lands.     --mortimer.
       1913 webster
   b to make dull- or sad-colored, as cloth.
   c to make grave or serious; to make melancholy or
       sorrowful.
       1913 webster

             her gloomy presence saddens all the scene. --pope.
       1913 webster
see also:
saddened saddening 

saddening
     adj : causing or suggestive of sorrow or gloom; "a gloomy
           outlook"; "gloomy news" syn: depressing, depressive,
            gloomy
see also:
depressing depressive gloomy