Weeds in the Animal Crossing series are small clumps of grass that change color according to the seasons. Three new weeds appear in the player's town each day at 6 AM. In New Leaf the player (as mayor) can put in effect the beautiful town ordinance, lessening the chance of weeds.
Effects on the town
Weeds do not necessarily have to be pulled up but will affect the town's environment. Forgetting to pull out the weeds for a long period will result in the appearance of a rafflesia, a large, red flower which attracts flies, further lowering the town rating.
Weeds are also contaminants as they will lower the chance of flowers breeding.
Effects on villagers
If a town contains a large number of weeds, villagers may comment about an abundance of weeds in the area. Isabelle (New Leaf) or Pelly/Phyllis (Wild World, City Folk) also comment on the player when asked about Citizen Satisfaction. The player can pull out weeds alone; however, Wisp is the only character able to uproot all weeds at once, but it will take a maximum of two weeks to complete. He is absent in Animal Forest and Wild World, and he no longer provides this service in New Leaf. In New Leaf, Leif replaces Wisp and once T.I.Y. is completed, offers a weed pulling service that only takes a day to complete.
Role in New Horizons
In New Horizons, weeds are redesigned to more closely resemble realistic weeds and can be plucked and collected as a clump of weeds. They can be stacked up to 99. One bag of weeds sells for 10 bells, or 20 bells when sold to Leif. Selling weeds can earn Nook Miles via the Greedy Weeder stamp card and Nook Miles+. Bags of weeds are used in some DIY Recipes.
Weeds spawn randomly while there is room for them to grow on the island, and are self-propagating. The type of weed depends on the season, and the stage of weed depends on a range of days the weed has gone unplucked. Early stage weeds have 3 different varieties, but they all become homogeneous as they reach full maturity. Unlike previous games, weeds do not affect the player's island rating until a certain threshold is reached.