A specialist in gardening or landscaping is who you hire to do the job. They can be self taught, a Master Gardener, certified nurseryman, horticulturist, landscape engineer, or combination of any of these.
Horticulturalist.
The ground area is the landscaping; the job you are doing is landscaping.
A flag specialist is called a vexillologist.
Gardening.
Interlocking brick is considered a part of landscaping. It is called hardscaping. When one works in this field, all sorts of 'landscaping'' is involved. The two go hand in hand
That would be xeriscapic landscaping. (those who say "zero-scaping" are pronouncing it wrong.)
botany
A bird specialist is called an orithologist
There are gardening magazines on the market that are focused specifically on organic gardening. One great magazine for organic gardening is called Organic Gardening.
a specialist in the study of substances attained by mining. its called mineralogist
Garderning and flowering respectively.
A skilled employee is called a professional while unskilled one is called an amateur.