If you do not see a particular plant on this list, the omission DOES NOT necessarily indicate the plant is not poisonous.
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 - hulls
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 I do have reason to believe that this plant MAY be toxic to fish from correspondence with ponder who lost a lot of fish that ate the cherries that dropped in her pond. Use caution on placing a pond under this tree.
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 I have a reported case of fish deaths after eating the flowers and leaves. Once the leaves and flowers were removed from the pond, and the water changed out, the fish stopped dying.

Hyacinth - bulbs
Jack-in-the-pulpit – all parts
Japanese laurel – all parts
Indian Turnip - all parts
Iris – leaves, roots, rhizomes
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 (from decks also)
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

ACONITUM (Aconite, Monkshood) roots, flowers, & leaves
Allamanda – all parts
Allspice- leaves,seeds
Alocasia leaves and stems
Aloe leaves
Amaryllis bulbs
Anemone – all parts
Angel Trumpet Tree (Datura Arborea) flowers & leaves
Anthurium all parts
Apple seeds contain hydrocyanic acid
Aprcot leaves
Atropa Belladonna all parts, especially black berries
Autumn Crocus (C. Sativus, Saffron Crocus) bulbs
Azaleas (Rhododendorn) Leaves
Balsam Pear Seeds, Outer Rind of Fruit
Baneberry berries, roots
Beach Pea (Lathyrus Maritimus) stems
Betel Nut Palm all parts
Bird of Paradise Seeds
Bittersweet (Celastrus) berries
Black Locust Bark, sprouts, foliage
Black walnut hulls
Bleeding Heart (Dicentra, Dutchman's Breeches) foliage & roots
Bluebonnets (Lupinus) all parts
Blue-Green Algae Some forms toxic
Bottlebrush (Callistemon, possibly Melaleuca) flowers
Boxwood Leaves, stems
Buckeye (Aesculus, Horse Chestnut) sprouts and nuts
Buckthorn Fruit, bark
Buttercup sap, leaves, bulbs
Cactus
Caladium – whole plant
California tern roots seeds
Calla Lily Leaves
Carolina jasmine – all parts
Castor Bean (Castor Oil) Beans, Leaves
Challice Vine All parts
Chenille plant
Cherry bark, twigs, leaves, pits
Cherry seeds contain hydrocyanic acid
Cherry Laurel (Prunus Varieties) all parts, seeds contain hydrocyanic acid
Cherry Tree Bark, twigs,l eaves, pits
Chinaberry (Melia Azedarach) berries are poisonous
Choke cherry – all parts, especially the cherries
Christmas Berry (Heteromeles Arbutifolia, Toyon) berries are poisonous
Christmas Candle Sap
Colocasia all parts
Columbine (Aquilegia) all parts
Common Privet (Ligustrum) black or blue wax coated berries and leaves
Coral Berry (Symphoricarpos) seeds
Coral Plant Seeds
Crpcus all bulbs
Croton seeds
Daffodil Bulbs
Daphne Berries
Datura (Brugmansia) flowers, berries, & seeds
Day lily very poisonous to cats
Deadly Amanita All parts
Deadly Nightshade (Solanum Nigrum) all parts, unripe fruit & foliage
Death Camas All parts
Delphinium All parts
Destroying Angel (Amanita Phalloides, Death Cup) all parts
Dieffenbachia Leaves
Digitalis – all parts
Dogwood (Cornus) fruit slightly poisonous
Dumbcane (dieffenbachia) – all parts
Easter lily very poisonous to cats
Egg Plant All parts but fruit
Elderberry (Sambucus) red fruit poisonous, black & blue fruit o.k.
Elephant Ear (Colocasia, Taro, Caladium) stem & leaves
English Ivy Berries, leaves
Euphorbia (Splurge, Gopher Plant, Mole Plant) roots, sap
False Henbano All parts
Fly Agaric (Fly Amanita Mushroom) whole plant
Four O'Clock whole plant
Foxglove Leaves, seeds
Gelsemium (Carolina Jessamine) whole plant
Gloriosa lily – all parts
Golden Chain All parts, especially seeds
Hellebore (Ranunculaccea) all parts
Hemlock (Tsuga) all parts, especially roots
Hemlock, water All parts, especially roots and seeds
Hemlosk, poison All parts, especially roots and seeds
Henbane Seeds
Holly Berries
Honeysuckle Leave, flowers
Horse Chestnut Nuts, twigs
Hyacinth Bulbs
Hydrangea Flower bud
Impatiens (Balsam, Touch-Me-Not, Snapweed) whole plant
Indian Turnip(Jack-in-the-Pulpit) All parts
Iris (Blue Flag) Bulbs
Ivy (Hedera) all parts
Jack-in-the-pulpit – all parts
Japanese laurel – all parts
Jasmine berries
Java Bean (Lima) Uncooked bean
Jerusalam Cherry (Solanum Pseudocapsicum) fruit & leaves
Jimsonweed Leaves, seeds
Juniper (J.virginiana) Needles, stems, berries
Lanbkill (Kalmia Angustifolia, Sheep Laurel) leaves
Lantana Immature berries
Larkspur (Delphinium) foliage & roots are dangerous, seeds may be fatal
Laurel All parts
Lily of the Valley All parts, including water
Lobelia leaves
Locoweed All parts
Locust bark,leaves, seeds
Lords and Ladies All parts
Lupine (Lupinus) seeds
Machineel all parts
Marijuana all parts
May Apple (Podophullum) all parts
Mescal Bean Seeds
Milkweed (Asciepias) all parts, especially sap
Misteltoe Berries
Moccasin FLOWER (Lady Slipper, Cypripedium Spectabiles) all parts
Mock Orange Fruit
Monkshood Leaves, roots
Morning Glory All parts
Mountain Laurek (Kalmia Latifolia) young leaves & shoots, can be fatal
Mushrooms wild types
Mustard – roots and seeds
Narcissus Bulbs
Natal Cherry (Solanum) berries
Nicotiana (Flowering Tobacco) leaves
Nightshades (all) Berries, leaves
Oak Acorns, foliage
Oleander – all parts
Oleaner Leaves,branches,nectar of blossoms
Peach, seeds
Pear, seeds
Peony (Paeonia) all parts
Periwinkle (Vinca, Myrtle) whole plant
Philodendron Leaves, stem
Pikeweed Leaves,roots,immature berries
Pine sap
Pinks (Sweet William, Carnation, Dianthus) all parts
Plum, seeds
Poinsettia Leaves, flowers
Poison Ivy Sap
Poison Oak Sap
Pokeweed (Phytolacca, Pokeberry) roots are dangerous
Poppy (Papaver) all except California Poppy can be dangerous
Potato Eyes and new shoots
Privet berries, leaves
Prunus (many varieties) seeds, some parts
Ranunculus all parts
Redwood sap (from decks also)
Rhododendron All parts
Rhubarb Leaves
Rosary Peas Seeds
Rosemary (Rosemarius Officinalis) leaves of certain varieties are poisonous
Sage (Salvia) leaves of certain varieties are poisonous
Scotchbroom (Cytinsus Scoparious) seeds, invasive
Senecio whole plant of some species
Skunk Cabbage All parts
Snapdragon all parts
Snow Drops All parts, especially bulbs
Snow on Mountain All parts
Solanum (Nightshade) all, especially some berries
Squirrel Corn (Dicentra Canadensis, Bleeding Heart) all parts
Stramonium (Jimson Weed, Datura) all parts
SUMAC (Rhus) all parts
Sweet Pea Seeds and fruit
TANSY (Tanacetum) all parts
Taro – all parts
Tiger Lily all parts
Toadstools can be fatal
Tobacco Leaves
Tomato foliage & vines
Trumpet vine – all parts
Tulip bulbs
Virginia Creeper Sap
Wisteria All parts
Yam Bean Roots, immature polds
Yew (American, English, Japanese) Needles, seeds

might of been a shorter list if you'd stated the plants that are okay near koi!!!

.................but thanks (i was only thinking of your rsi!)

iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii opps my fingers cramped lol no problems

koimaster wrote:iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii opps my fingers cramped lol no problems

Dohhh ! I'm STILL confused .........
I'm sure I've seen somewhere in print that all parts of Clematis are toxic to Koi .........
yet not on the list ?

I also want to make absolutely sure about the following :

Crocosmia Lucifer ?

Summer Jasmine climber ?

French Lavender ?

Petunia ?

Bamboo ?

Phormium ?

Hosta ?

Acer ?

Peter

i'l add a few aswell , better put my master's to some use

I read about Rhododendron and ponds ages ago, thanks for confirming it, but can you guess what I have overhanging my pond, what has been there for all the time I have had my pond since 1995, when I didn't know better - Rhododendron!!

I did lose several fish to some death in the spring, don't know what or why they died, a vet autopsied 1 of them, all we found out was she was a girl, a big girl at 2 ft I called her Quick Silver, can you guess her colour

I put it down to my filtration...but it was the same filtration I have had for years - just like the Rhododendron , so maybe I will never know.

I guess you did say a list of possible poisonous plants, so I am being pedantic - right word?? My wife would just call me her Jammy Dodger for getting away with my fish living near Rhododendron when others have keeled over

My mum has bamboo near her pond.

this list i dont think has been confirmed by a koi vet but i wouldn't risk it

as and when and if I ever enlarge my pond they can go. I can't even get to them at the moment without a bit of stepping here and arm twisting there, but if I can, might be worth cutting them back a bit, they not to big. I have a dogwood near as well, sod that on your list as well. Just fill the pond in