Answer: First off, check with your utility company to see if they have set back requirements or limitations on what you can do near the box. Some have legally required access that prevents close planting.
Also be sure you know where any underground lines are. In most areas, you must call before you dig and have all utility locations verified -- before you dig in your yard -- to prevent accidental damage to any underground utilities (and for your own safety.)
You may find the most effective concealment is achieved by planting a cluster of several shrubs in front of or to one side of the box. You might use a plant that you have planted elsewhere in your landscape for a sense of continuity. For example, if you have junipers in your landscape you might repeat those same shrubs near the box. Or, if your concern is primarily curb appeal, you might place a section of fencing in front of the box and use that as a backdrop for a planting bed of shrubs and/or hardy perennials. But again it is important to integrate it into your overall landscape. Otherwise, you will end up attracting attention to the box rather than decreasing its visual importance.
Your actual plant selection should be based on the space available for them to grow into, the amount of sun or shade (and time of day it is sunny/shady), wind exposure (especially in winter) as well as soil type. Your local professionally trained nurseryman should be able to help you evaluate the growing conditions and identify plants that would thrive there as well as meet your design goals.
While I am not able to give you specific plant recommendations, I hope this helps you begin your planning.
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