As a designer I am concerned with several things.
The best plants in the best spot.
The interaction the client wants to have with the garden. How the client is going to use the garden. How much work one does or doesn’t want to do in the garden.
How the garden looks from the house all year including winter.
Do you want to compost or incorporate edible or native plants?
Sometimes gardens are underplanted and huge space is left between plants. The thought there is we are waiting for the plants maximum potential. I favour a different style where we plant closer together. This is a more finished look sooner, and there are less weeds and less water needed.
There is a concern with plants getting crowded and overtaking other plants. This is not a problem, plants touching… it is easy to maintain the integrity of each plant and still let them blend together in a garden … sometimes all that is needed is pruning or in the case of perennials dividing and moving.
The spring time work load with a Calgary perennial and shrub garden requires more work in the spring and fall … cutting back the dead of the perennials, weeding and removing dead leaves … but you will be rewarded all year long.