Poisonous Plants for a Koi Pond

While there is no definitive list of all plants that have a toxic effect on koi, many koi enthusiasts and societies have placed lists of their own findings on the Internet (see References). It's important to realize that many plants contain toxins as a defense mechanism, and if these toxins are harmful when human beings and small animals consume them, then koi may also suffer through contact with water the plants have touched.

  1. Bushes and Trees

    • The berries, fruit, and pods of some bushes and trees are toxic to all animals, and especially to koi, which are small and react to lower amounts of toxins. Gardeners often grow daphne mezereum because it has attractive flowers, for example, but its berries contain daphnetoxin, which inhibits blood circulation.

    Vines

    • All parts of the Dutchman's pipe vine (Aristolochia durior) are toxic to koi, as are the leaves and berries of the wisteria sinensis and wisteria floribunda vines. Dutchman's pipe contains a nephrotoxin that destroys kidneys, and wisteria affects the nervous system. Grow these vines far from a koi pond to prevent accidental poisoning.

    Perennials

    • Many perennials are dangerous, and often all parts of the perennial are toxic, instead of the berries or leaves alone. For example, koi owners should be wary of the lily of the valley (Convollaria majalis), which is so harmful that even the water from the vase can kill koi. Wolfsbane (Aconitum) also contains a powerful neurotoxin that can poison the water it touches.

    Nightshades

    • Nightshades contain the poisonous compound solanine, which is harmful to human beings in large amounts. Tomato plants, potato plants, and deadly nightshade, for example, are all plants of the nightshade family, and they will all poison koi if the koi consume them.

    Other Plants

    • Many other plants have toxic effects on animals, and so it's always important to check a toxicity database before introducing koi to a garden (see Resources).