It is not safe to assume that any plant is safe for guinea pigs to eat. Some plants can be toxic, causing serious illness or even death. Ground elder is a common plant in gardens, but its safety for guinea pigs is not well-established.
Here's what you should do instead:
* Consult a veterinarian: They are the best source of information regarding your guinea pig's diet.
* Stick to known safe foods: Offer your guinea pig a diet primarily consisting of fresh hay, Timothy hay, and a small amount of fresh vegetables and pellets specifically formulated for guinea pigs.
Remember, your guinea pig's health is paramount. It's always best to err on the side of caution and consult a veterinarian before introducing any new foods to their diet.