Why do cats like to nibble grass?

Even though cats are obligate carnivores and don’t usually volunteer to eat fruit or vegetables, they do like to eat grass.

Eating grass is a normal behaviour in cats yet not fully understood – the general understanding is that it helps to move food or hairballs through the digestive tract (either up or down as grass-eating often results in vomiting). It may also provide them with essential trace elements in their diet, so it is recommended that cats without access to grass outside are provided with a source indoors. This can be a commercial pack of ‘cat grass’ or a pot in which grass seeds or grass from the garden can be grown.

Indoor cats without access to grass may chew other potted plants they would usually ignore or avoid and which may be poisonous. 

List of Toxic Plants: 

Houseplants

Amaryllis
Aphelandra
Azalea
Castor Oil Plant (also see Ricinus)
Christmas Cherry (also see Solanum)
Chrysanthemum (also see
Dendranthema)
Codiaeum
Croton (also see Codiaeum)
Cyclamen
Devil’s Ivy (also see Epipremnum aureum)
Dieffenbachia*
Dumb Cane (also see Dieffenbachia)
Elephant’s Ear (also see Alocasia,
Caladium)
Epipremnum aureum
Ferns
Holly (also see Ilex)
Hypoestes phyllostachya
Hyacinthus
Ivy (also see Hedera)
Kalanchoe
Mistletoe (also see Viscum)
Nerium oleander
Oleander (also see Nerium oleander)
Ornithogalum
Senecio
Star of Bethlehem (also see Ornithogalum)
Umbellatum
Umbrella Plant (also see Schefflera)
Zebra Plant (also see Aphelandra)