While flowers may add color and scent to the pond area, many are extremely toxic to fish and frogs. They include amaryllis, anemone, bird of paradise, bluebonnet, buttercup, calla lily, daffodil, jonquil, juniper, lily of the valley, narcissus, poinsettia, morning glory, tiger lily and snapdragon flowers.
Many trees also can be toxic to pond wildlife. The sap, bark and leaves can kill fish when they fall into the pond. Some poisonous trees for ponds include horse chestnut, pine, black walnut, cherry, redwood, oak and yew trees.
Just as some berries are toxic to humans, they can also be hazardous to pond wildlife. Some toxic berries include privet, baneberry, holly, jasmine, lantana, datura, English ivy and mistletoe berries.
Some people believe that different parts of vegetable plants can be toxic to pond fish as well. Rhubarb leaves, eggplant stems and leaves, potato roots and eyes, sweet pea seeds and tomato leaves are thought to be poisonous to koi.
Bushes, Vines and Miscellaneous Plants
Many parts of bushes and vines can also be deadly to pond wildlife. Some include larkspur, flowering tobacco, castor beans, climbing nightshade, elephant ears, wisteria vines and ginkgo.
Typically, having algae growth in the pond is very helpful to the wildlife. When it blocks the light to the underwater plants and begins to take over, it can change from useful to toxic.