First, I have no veterinary background so my answer is based on the knowledge gained through a lifetime of dog ownership.
Vomiting after eating grass, especially coarse couch grass, is recognised as normal behaviour.
My dogs also love to eat small amounts of growing cereal crop leaves when they are at their most tender in the spring.
A few minutes afterwards, they sometimes vomit a ball of vegetation covered in frothy saliva.
Some think this is nature’s way of getting rid of excess digestive juices which can accumulate in an empty stomach.
My dogs, which are all kennelled, are more likely to do this when they first come out for exercise rather than after they have been fed.
They will also eat fine grasses and other vegetation in small quantities that pass through their system with no ill-effect.
It is noticeable as fibres in the stools because it has only been partly digested and may be a way of cleansing the animal’s bowels.
In the Herbal Book for the Dog, the author states: “Couchgrass eating should always be encouraged; the ‘rake’ action of the grass in removing mucus and other internal impurities is very healthful”.
However, if the vomiting in your dog gets worse and is not just associated with eating grass, then veterinary advice should be sought.
My eight-year-old Labrador bitch is sick after eating grass