These flowers can be used for crafting Poison Bombs in your Crafting Menu opened with "q" as the default key (or at any Crafting Table in older worlds). Weepwood Flowers can also be used as an ingredient in Basic Health Potions, Stone Mining Cells, Taming Collars, Golden Potions and Stamina Regeneration Potions - in crafting-recipes that will accept any kind of Flowers. They glow very faintly, so they cannot really be used as a light-source. If placed into Flower Pots, Wood Planters or on Wall Shelves, these flowers will not make any mobs spawn though.