Lethal. Fireflies produce lucibufagins — defensive steroids that are acutely toxic to leopard geckos. A single firefly has killed geckos in documented cases. There is no safe amount and no antidote. This applies to all firefly species regardless of whether they appear to glow. Never feed any wild-caught insect.

Any insect from your garden, field, or outdoor space carries pesticide residue, herbicide contamination, and parasite risk (pinworms, flagellates, and others are common). There is no way to test or clean a wild insect sufficiently. Only ever feed captive-bred insects from a reputable supplier.

The entire Euphorbia genus is unsafe. All species produce a milky latex sap that is highly toxic and causes severe burns, swelling, and potential blindness on contact with eyes or mouth. The sap sprays when branches break — a realistic risk in an active gecko enclosure. Common dangerous species include: Pencil Cactus (E. tirucalli/Firesticks), African Milk Tree (E. trigona), Dragon Bones, and Poinsettia (E. pulcherrima). No Euphorbia species should be used.

Extremely common houseplant sold everywhere — and toxic to reptiles. Contains bufadienolides (cardiac glycosides) that can cause serious cardiac issues. Do not confuse with Walking Kalanchoe (K. synsepala), which is safe. If you see 'Kalanchoe' with flowers in a supermarket or garden centre, assume it's this species.

Widely listed as 'reptile safe' on general pet sites because it was assessed for dogs and cats — it is not safe for reptiles. Reptiles Magazine's toxic plant list includes Pothos. It also requires humidity levels that are incompatible with a leo enclosure. Avoid.

All philodendrons contain calcium oxalate crystals that cause irritation and swelling of the mouth and throat. Toxic to reptiles per Reptiles Magazine. Also requires high humidity incompatible with leo husbandry.

Widely listed as 'reptile safe' on general pet sites because it was assessed for dogs and cats — it is not safe for reptiles. Reptiles Magazine's toxic plant list includes Pothos. Also requires humidity levels incompatible with a leo enclosure.

Contains calcium oxalate crystals. Toxic to reptiles. Also a moisture-loving plant that would rapidly push humidity far beyond the 30–50% a leo needs.

All ivy species on the Reptiles Magazine toxic plant list. Contains triterpenoid saponins and falcarinol, both toxic on ingestion. Common in gardens and sold as a terrarium plant — do not use.

Extremely toxic to virtually all animals. Contains cardiac glycosides (oleandrin) that cause heart failure. One of the most dangerous ornamental plants in existence. Never place near any reptile.

Spines puncture and cut reptile skin even through scales. Eye injuries are particularly common and serious. If you want a cactus look, use spineless succulents like Haworthia or Gasteria instead. Some smooth-stemmed cacti like Rhipsalis are safe — but standard spined cacti are not.

Note: despite being in the Senecio genus like String of Pearls and String of Bananas, ragwort is a completely different and highly toxic plant. Contains pyrrolizidine alkaloids that cause liver failure. Common in UK gardens and grassland. Never introduce it to any enclosure.

Contains grayanotoxins which disrupt sodium channels and can cause cardiac issues. On Reptiles Magazine toxic plant list. Common garden shrub in the UK — keep enclosures away from it.

One of the most toxic plants to animals. Every part — seeds, leaves, roots — contains cycasin, which causes severe liver failure. Despite looking like a harmless palm, even a tiny amount ingested can be fatal. Never use near any reptile.

Most Dracaena species — D. marginata, D. fragrans (corn plant), D. reflexa — contain saponins toxic to reptiles. Note: Dracaena trifasciata (snake plant, formerly Sansevieria) is safe and listed separately. Do not assume all Dracaena are interchangeable.