Answer: Here are the facts. I hope this clarifies things for you. Plant taxonomy classifies 'Emerald Green' Arborvitae under Thuja occidentalis. 'Emerald Green' arborvitae is one of its cultivars. 'Emerald Green' arborvitae is an evergreen in the Cypress family. Although some might say they are, technically, tall shrubs, they are commonly referred to as "trees."
'Emerald Green' arborvitae usually reaches just 12'-14', with a spread of 3'-4'. Its foliage comes in flat sprays and, if you look closely, the needles appear covered in scales.
If the typical dimensions for this plant are too big for your needs, they can be pruned in early spring (before any new growth) to a size with which you are more comfortable. Since this tree is not drought-tolerant, water well during hot summers and mulch generously to hold in some of that water.
Although not drought-tolerant, 'Emerald Green' arborvitae does fine in full sun (it doesn't mind partial shade, however). Grow in a well-drained soil.
A slim tree of medium height, 'Emerald Green' arborvitae is often planted in a row -- as a decorative border planting, wind screen or privacy screen. Because it is evergreen, its usefulness in any of these capacities extends throughout the year in the North. Occasionally, the tree is also used as a specimen.
Its cold hardiness makes 'Emerald Green' arborvitae a solid choice for Northern landscapers, who might otherwise use Leyland cypress, a favorite in zone 6 and higher. 'Emerald Green' arborvitae would also be the choice over Leyland cypress in cases where a tall tree would be inappropriate. Whereas the latter reaches at least 60' at maturity, 'Emerald Green' arborvitae usually reaches just 12'-14'. These differences notwithstanding, the two trees have a similar look and are both popular, particularly as "living wall" privacy screens.
I hope you planted 4 feet apart rather than 4 inches as mentioned in your question! The ultimate size of your arborvitaes will depend upon growing conditions. In cold winter regions such as yours, expect an average height of about 14'.
Hope this answers all your questions!
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