Misinformed & Bad Choice

(1) All woody species (vines, shrubs & trees) are indeterminate growers (i.e., they do not stop growing {getting bigger} unless dormant, until dead, and some species may live many decades or centuries). Eastern White Cedar (AKA arborvitae) Thuja occidentalis is no exception. It is a tree; a potentially very big tree. I have observed ancient specimens in Michigan 75+ feet tall with trunks well over 4 feet in diameter! The "mature size" listed on most plant labels is usually intended to be the ten-year average size. There is NO full grown (mature) size. The maximum possible size is determined by the genetic constitution of the species/cultivar, how planted, where planted, the growing conditions and how long the specimen lives, which also varies by species/cultivar.

(2) Eastern White Cedar is a swamp plant and can be a great landscape plant--one of my favorite species. The natural haunt of this northern native is low land. It prefers moist ground--White Pine (Pinus spp.) just the opposite. In Michigan and Wisconsin one would expect Arborvitae in the swamps, and White Pine on the higher and drier ground. Arborvitae will tolerate drier conditions once established but that can take several years. Recently planted specimens are vulnerable to dying from water deficiency. They must receive regular and ample supplement water, especially in summer and fall, or they will brown and once brown are dead--they will not recover. And, if they live, as I previously noted, they can get too big and any lower branches that touch the ground are likely to produce roots.

(3) The answer to blocking a utility box or other hard feature is often NOT a plant. I often recommend a fence or trellis, especially one that can be easily removed if the utility structure needs maintenance. A hardscape future provides immediate remedy that will not get bigger, nor will be die, but it may require occasional maintenance. NOTE: there is likely an easement around where the structure is located that prohibits you from planting too close, or with the wrong kind of plant, or without permission. Moreover, whether plant or hardscape feature, an 811 call to discover and avoid underground lines is a must.

I presume the planting in the featured pic was done by the homeowner. If a "professional landscaper" did it, and I would not be surprised, their name ought be added to the list of DO NOT USE THIS PERSON OR COMPANY. I recently gave a lecture on common gardening mistakes. This example is one of them. Your idea does not mean it is a good idea.