| Common Name | Botanical Name | Details |
| Ceriman | Monstera deliciosa | Causes diarrhea and oral irritation if eaten. May cause dermatitis. |
| Cherry (kernels) | Prunus species | Kernels contain cyanide. |
| Christmas Rose (leaves & roots) | Helleborus niger | Harmful if eaten in quantity. |
| Chrysanthemum (leaves & stems) | Chrysanthemum species | May cause dermatitis. |
| Clematis | Clematis armandii | Gastrointestinal tract and nervous system affected by plant toxins. May cause dermatitis. |
| Cocoa (husks or mulch) | Similar effects to that of chocolate - hyperactivity, increased heart rate. | |
| Corn Cockle (seeds) | Agrostemma species | Harmful if eaten in quantity |
| Cuckoo Pint | Arum maculatum | Toxic if eaten, causing nausea and vomiting. May cause a skin allergy. |
| Cyclamen | Cyclamen species | Gastrointestinal tract affected. Convulsions and paralysis. |
| Daffodil (bulbs) | Narcissus species | Diarrhea, vomiting, nausea. May cause dermatitis - Can Be Fatal |
| Daphne | Daphne species | Gastrointestinal tract and kidneys affected. May cause dermatitis |
| Deadly Nightshade | Atropa belladonna | GToxic if eaten, causing nausea and vomiting. |
| Delphinium | Delphinium species | Harmful if eaten in quantity. |
| Devil's Fig | Solanum hispidium | Harmful if eaten in quantity. |
| Dieffenbachia | Dieffenbachia species | Diarrha and oral irritation if eaten. May cause dermatitis, tremors, seizures, loss of balance, asphixia - Can Be Fatal |
| Dragon Tree | Dracaena species | Vomiting and diarrhea. |
| Dumb Cane | Dieffenbachia amaena | Diarrha and oral irritation if eaten. May cause dermatitis, tremors, seizures, loss of balance, asphixia - Can Be Fatal |
| Dwarf Morning Glory | Convolvulus tricolor | Harmful if eaten in quantity. |
| Easter Lily | Lilium longiflorum | (Especially poisonous to cats) |
| Echium | Echium species | Harmful if eaten in quantity. May cause a skin allergy. |
| Elderberry | Sambucus canadensis | Nausea and vomiting. |
| Elephant Ears | Bergenia species | Intense burning, irritation and swelling of the mouth and throat. If tongue swells enough to block air passage - Can Be Fatal |
| English Ivy (leaves & berries) | Hedera helix | Gastrointestinal tract affected. May cause dermatitis. |
| European Spindle | Euonymus europaeus | Harmful if eaten in quantity. |