go to seed

verb2

1. •
   To pass from flowering or ripening to the formation of seeds.

   • Wild tomatoes, which had gone to seed or been remorselessly hoed out from the beginning of Berande, were foraged for salads, soups, and sauces. — 1911
2. •
   (figurative) To deteriorate; to decline into an unkempt or debased condition.

   • 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. — 1898