There are several plants that may harm dogs. These include Bulbs (e.g. Lily, Daffodil), Ferns, Flowering plants, Garden Perennials, House Plants, Lilies, Shrubs, Succulents, Trees, Vines and other miscellaneous kinds of plants including American Bittersweet, Bird of Paradise, Florida Beauty, Fruit Salad plant, Gold Dust, Hurricane Plant, Castor Bean, Clematis and Mexican Breadfruit etc.
Two of the most common and most dangerous plants are lilies and poinsettias. They are both highly poisonous to animals. To find more common plants that is dangerous to your dog at http://www.entirelypets.com/toxicplants.html.