I used to work in a long-term care facility and it had a garden for the residents to care for, and it was the best therapy for them! The problem with bending over can be overcome, but it would take some work. Their gardens were in highly raised beds so even the wheel-chair bound residents could participate. Even if your mother is not ready for a wheel chair, she could get one of those cane-stools and sit while tending her garden, and easily move it around as she worked the beds. They grew all sorts of vegetables, herbs and flowers...and were fortunate to be able to eat the 'real' food as opposed to most nursing homes which serve horrendous slop that I wouldn't feed to a pig!