My Mom loves to work in her garden. What durable/safe garden bench/chair would you recommend for her?

Not too stable on her feet. My mom is in her mid-80s and has always enjoyed gardening. Now that the weather is nice, she yearns to get outside and work in her yard. However, she has balance issues, cannot stand up for very long, knees are bad too. Although she appreciates it when I take-over the things she used to do, she gets very sad when she realizes that this is one more thing her body forbids her to do. She is never alone; I am there all the time too.

Is there a chair or bench that would be good for her to use in the garden- dirt, mud, etc ? Something strong, safe that she could use as an aid? Again, she is not left unattended. Thanks very much.