For my first house, I designed and installed the gardens myself (except for the lawn and the sprinkler system). It was beautiful. But it was also a high-maintenance landscape. Sometimes, I would work in the garden by the light of a full moon because there was just not enough daylight to do everything that needed doing.
For my second (and current) house, I had a design developed by a not-to-local local nursery. If I bought enough materials there (not only plants but hardware too), the cost of the plans was refunded. (More than 30 years later I still shop at that nursery.) The designer visited my house to check the dimensions of the front and back yards, the compass orientation of the property, and existing features (block walls, patio slab, etc). Then, we discussed what I like and dislike. When I saw the draft of the plans, I told the designer what needed changing. After having the lawn and sprinkers installed, I did everything else. It too was beautiful, and it was much less of an effort to maintain. For over
25 years, I generally followed those plans.
However, one feature of this do-it-yourself landscape was a shade tree in the back yard. It grew so large that plans for a garden in the sun were no longer appropriate; see my . Thus, three years ago, I had a new landscape design created for the back yard. The design incorporated existing trees and some of the existing shrubs (especially my roses and camellias). But it also reflected the fact that very few parts of the garden have full-day sun. Then, since I was already in my 60s, I had the designer (a landscape contractor) install the new design. Again, it is beautiful. Now that it is established and the weeds are under control, the major maintenance effort is grooming to remove spent flowers, pruning the roses and peach tree, and calling the lawn service twice a year to mow the ornamental red fescue. I actually do more than that; but I'm now retired and can take time during the week to renovate a bush by cutting it back severely, replace a dead plant, or fuss with potted herbs. (My gardening diary is at .)
Should you use a professional to design your garden? Definitely, unless you are willing to accept the reality that mistakes mean extra ongoing work.
Should you use a professional to install your garden? If you not only have sufficient money and also are too old or tired to do it yourself.