Toxic Plants to Fish - Possiblities

While many plants are listed as toxic to fish, some of these plants have been in our ponds for years without any problems. Water Iris is one that is listed as toxic, but we have had water iris in our ponds without problems. Koi are omnivorous and will eat plants. The key is to provide plants koi will eat and are good for them. Watercress is very nutritional for koi with almost the same minerals and vitamins as spirulina algae, and the koi love it. It grows fast enough to keep up with the appetite of the koi if planted properly. Watercress should be planted shallow where there is plenty of water flow. Place rock boulders around the plant to protects the roots, otherwise the koi will uproot the plant. The plant will grow over the rocks and give the koi a good food source. We highly recommend watercress be included in any koi pond that has plants.

Allamanda – all parts
Aloe - leaves
Alocasia - leaves and stems
Allspice- leaves, seeds
Amaryllis - bulbs
Anemone – all parts
Anthurium all parts
Apricot - leaves
Azalea – all parts
Baneberry - berries, roots
Bird of Paradise - seeds
Black Locust Bark - sprouts, foliage
Black walnut all parts  confirmed reports of death
Boxwood - leaves, stems
Buttercup - sap, leaves
Cactus
Calla Lily - leaves
California tern roots seeds
Cardinal flower – all parts but I have not found that to be true
Carolina jasmine – all parts
Caladium – whole plant
Cherry - bark, twigs, leaves, pits
Chenille plant
Choke cherry – all parts
Colocasia - all parts
Coral Plant - seeds
Croton - seeds
Daffodil - bulbs
Datura - all parts
Day lily – very poisonous to cats
Delphinium – all parts
Death Camas - all parts
Dumbcane (dieffenbachia) – all parts
Digitalis – all parts
Easter lily - very poisonous to cats
Elephant's - ear all parts
Eggplant - all but fruit
Elephants Ear - leaves, stem
English Ivy – all parts 
Foxglove – all parts
Gloriosa lily – all parts
Hemlock - all parts
Holly - berries
Honeysuckle - all parts
Hyacinth - bulbs
Jack-in-the-pulpit – all parts
Japanese laurel – all parts
Indian Turnip - all parts
Iris – leaves, roots, rhizomes (We have had water iris in our ponds for years and have not had any problems.)
Jasmine - berries
Java Bean - uncooked bean
Lantana – all parts
Larkspur – all parts
Laurel - all parts
Lily of the valley- all parts toxic to cats
Lobelia - leaves
Locust - bark,leaves, seeds
Locoweed - all parts
Lupine – all parts
Marijuana - all parts
Mayapple - all parts
Mimosa – all parts
Mistletoe - berries
Mock Orange - fruit
Morning Glory - all parts
Mustard – roots and seeds
Narcissus – bulbs
Nightshade
Oak - acorns, foliage
Oleander – all parts
Peach- leaves
Philodendron – all parts
Pine - sap
Poinsettia - leaves, flowers
Potato - eyes, new roots
Privet - berries, leaves
Prunus varieties - seeds, some parts
Ranunculus - all parts
Redwood - sap
Rhododendron – all parts
Rhubarb - leaves
Snapdragon - all parts
Snowdrop - all parts
Taro – all parts
Tiger Lily - all parts, especially to cats
Tomato - leaves
Trumpet vine – all parts
Tulip - bulbs