Yes, you can., but we must remember to use "an ample garden" and not just "ample garden". The meaning you are looking at is definition 1.1 in the Oxford Dictionary: large and accommodating. One example given there is: "People who have a modest home with an ample garden will be able to accommodate this breed."

ample is used for quantity(numbers). So if you have a large(big) AMOUNT of gardens... say 5 gardens...(that is a lot of gardens) so I can say. I have an ample amount of gardens.