IDIOMS

go to seed

(figuratively, by extension) To deteriorate; to decline into an unkempt or debased condition.

Example: 1911, Jack London, Adventure,
  Wild tomatoes, which had gone to seed or been remorselessly hoed out from the beginning of Berande, were foraged for salads, soups, and sauces.
1898, Eliot Gregory, Worldly Ways and Byways,
  But the "frump" will let herself and all her surroundings go to seed, not from humbleness of mind or an overwhelming sense of her own unworthiness, but in pure complacent conceit.
1919, Jerome K. Jerome, All Roads Lead to Calvary,
  But suppose I hang about till eighty and die a childish old gentleman with a mind all gone to seed.