JoB is right, you need specific lists for the animals you are worried about. Some animals have both sensitivities and tolerances very different to those of humans. The amount of spinach in a serving suitable for a human would severely damage a sheep; goats, geese and donkeys can tolerate doses of opium poppies that might kill a human, and we all know about dogs and onions or chocolate. Many dogs or cats which are raised indoors simply don't know about plants, and will eat anything. A friend's cat poisoned itself by gnawing on a Spathiphyllum (Peace Lily) grown as an indoor plant.
Knowing a bit of basic botany helps, even just enough to determine the family to which a plant belongs. For example, there are only a few poisonous plants in the Rosaceae, the Rose family, and those few are all easily identified, whereas with the Solanaceae (the tomato and tobacco family) you need to be very sure of your identification, because the family includes both edible and poisonous plants, plus some plants such as potatoes where some parts are edible (the tubers) and other parts can be poisonous ( the sweet and attractive fruits of potatoes and any green part). The Liliaceae family also needs caution - while some members such as onion, garlic and shallots are harmless, the bulbs of these may be confused with daffodils, jonquils, snowdrops and amaryllis which are very poisonous indeed. As a general rule, don't plant ornamental bulbs among your root vegetables.
The Euphorbiaceae (spurge family) produce a milky latex which can be an irritant poison and a local allergen both for humans and animals. Not all of this family are poisonous, but it's sensible to be careful around anything with milky sap until you know what it is. Speaking of allergens, many pets, like humans, have plant allergies, mostly skin reactions and hay fever, to plants including tradescantia and a number of grasses. The buttercup family (Ranunculaceae) also contains a number of garden ornamentals which are very poisonous, including larkspur, aconite and the hellebores.
And yeah, I do check each new unfamiliar plant, even though I am an old and experienced gardener, because I am a cautious person. That said, your Irises are unlikely to be a problem. Hopefully the local kids are unlikely to dig up the rhizomes and munch on them. They are woody and taste vile, and you need rather a lot to poison someone, unlike, say, oleander, daffodil bulbs, aconite or castor oil plant. I know someone who as a small child was poisoned by playing with castor beans and then sticking his fingers in his mouth - the seeds are shiny and pretty and his parents had no idea they were dangerous. He was very ill, and as a middle-aged man still has gut problems from the experience. So a degree of caution is warranted. But don't let it spoil your pleasure in gardening! Common sense is usually enough to keep you and yours safe. Basically the same rule I teach my foraging classes: if you don't know for certain sure that it is safe to eat, don't put it in your mouth!
