Koi Ponds and Trees, Plants and Shrubs to Avoid | Poison. Beware.
QUESTION ... What plants, shrubs and trees are poisonous to Koi and I should avoid putting around my Koi pond?
Jon Maynard, Tyne & Wear
ANSWER ... Trees to avoid near a Koi pond are the Laburnum (all vareities contain the alkaloid cytisene), the Yew Taxus (also contains an alkaloid that is a valuable aid in the treatment of cancer) , Willows Salix (contain salicylic acid, thats asprin, in all parts of the plant), Oak (because of tannins in the leaves), Poplars and possibly Elder.
Shrubs to avoid at all costs are Laurel, Guelder Rose (Viburnum opulus) and many of the brooms (Cytisus species) and Daphne despite its beautifully scented flowers.
Out of the perennials, here are some of the more unwelcome pondside visitors:
Aconitum - Monkshood
Arum - Cuckoo pint.
Colchicum - The autumn crocus
Convallaria - Lily of the Valley
Delphinium - All parts highly toxic and can be fatal if eaten
Digitalis - Foxgloves best avoided next to the pool.
Gloriosa superba - The beautiful Gloriosa Lily!
Lantana - Now very popular in the summer border or planted tub!
Phytolacca - The poke weed
Ricinus communis - Castor Oil Plant. Not to be confused with Fatsia.
Veratrum - The false Hellebore.
There are other plants that contain irritant saps and toxins in there leaves, but usually many of these will not present a problem if you keep your garden tidy and cut back your perennial plants at the end of the season.