Answer: Since you mentioned that a fence would not work due to snow, I think the same problem might occur with peonies or most shrubs -- they will not be tall enough. They may also suffer from winds in an exposed location. You might look into some of the larger plants that are often used in windbreaks and see if any of these appeal to you. Lilac suggest itself, it is sturdy and easy to grow and the blooms are lovely. I think a child might remember to "stop at the lilacs", it is such a pleasant association. The thorny rugosa roses might also be a possibility. On the other hand, small children are unpredictable and need careful watching, especially with heavy trucks close by. Keep in mind your son will begin to understand better about the danger of trucks in just a few short years -- probably by the time the shrubs begin to mature and create an effective barrier. Your local county extension and/or professional nurseryman may have other suggestions based on a more detailed understanding of the planting site and your goals -- and also your budget since a large number of plants will be needed. Good luck with your project.
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