Ask Mr. Smarty Plants

Mr. Smarty Plants thinks you have a reasonably good choice there.

Pinus strobus (Eastern white pine) has a native population in North Carolina; however these natural stands appear to be primarily to the west and in the great Smokey Mountains.  Depending on how clayey your soil is, you are correct to be concerned about how successful they will be.  The plant record for the Eastern white pine indicates that its native habitat is upland, mesic sand or loam sites, north slopes, or rocky stream banks.  The soils that they like are fertile, moist, well-drained soils, and like most pines they prefer an acidic soil.  Do you have other pines living close successfully?  If so, then the Eastern White Pine will likely do just fine there, especially if you give them loving care in the first two to three years as they establish themselves.

                   
       Pinus strobus                             Pinus strobus

 It strikes me that if the County is selling the trees, that is a fair indication that they can be planted successfully and also that you have  knowledgeable people to ask about the success of growing that tree in your local area!  However, if the folks selling the trees appear to be less than knowledgeable – you may want to go directly to the County Extension office.  The Union County Extension has a nice website here.

You should have planting instructions that come with the trees. If not, here are the basics:

Dig the hole as deep as the tree is planted in its container. Make the hole wide so the roots will have plenty of room to grow. Cover the hole back with the original soil, mulch with some compost, making sure the mulch is pulled back 2 inches from the base of the tree. Water thoroughly and deeply.