Some garden designers do nothing but planting design (and stray away from hard-landscape design) whilst most landscapers don't have an interest/knowledge in planting and it gets omitted from their schemes in favour of more hard-landscaping.
Unfortunately, a good percentage of clients also have planting low on the priority list when it comes to the garden design brief and an awful lot of schemes get built that are under-planted or have no plants at all.
The inclusion of planting in a scheme is a "must" for me as it never fails to amaze me about how much better a scheme looks as soon as the plants go in (no matter how good the hard-landscaping).
Planting "softens" the scheme, rests the eyes and provides ever-changing all-year-interest in the garden. It also helps provide shade, privacy, shelter and attracts wildlife as well as soaking up surface-water run-off from the paving.
Being educated in horticulture I have a passion for all types of planting and can design planting schemes to suit all tastes and budget.
If you wish to know the names and positions of all plants in a design prior to work on-site, I can produce a "Planting Plan" for your contractor. These are very time-consuming/expensive to produce so as a cheaper option I favour a service where the client simply provides the funds to buy the plants (say £1000) and I source suitable plants from local nurseries and plant them on their behalf (labour costs additional).