Evergreen arborvitae make excellent hedges and specimen plants when placed in the right location. They need full sun and protection from freezing winter winds. Arborvitae have a rounded or pyramidal form, depending on the variety. Arborvitae range considerably in size when mature from landscape plants that stand 8 feet high, to 45-foot-high specimens. Select a 6-foot specimen that will fit your landscape when mature and follow good planting and care practices.
Whether the arborvitae is in a pot or burlapped, dig a hole as deep as the top of the root ball, or the top of the soil in a pot so the plant sits in the soil at the same level that it sat at the nursery. Planting arborvitae too deeply may cause the roots to rot; planting it too shallowly may cause the roots to dry out. Set the plant in the hole gently and lay a yard stick across the rootball, extending to the surrounding ground. The yard stick should lay evenly.
Dig the hole at least 12 inches wider than the width of the root ball. Digging the hole wider loosens the soil to allow plenty of room for roots to spread out. If the soil is very hard clay, make the hole an extra 12 to 18 inches wide. By loosening poor, heavy soil, the arborvitae roots have a better chance of becoming established.
Giving exact measurements for how deep to dig a hole for a 6-foot arborvitae is impossible because the root balls vary so much in size. A typical pot for an arborvitae might hold 10 to 15 gallons of soil and stand 20 inches high by 20 inches wide. In this case, dig the hole 20 inches deep by 30 or 40 inches wide. Balled and burlapped trees may have a root ball 15 to 20 inches high by 15 inches wide. Dig the hole 20 inches deep and 25 or 35 inches wide. Eyeball it if you feel confident, or use a yard stick to measure the depth and width of the hole.
In general, no amendments are needed when digging the hole for arborvitae. Unlike most evergreens, arborvitae tolerate moist, low-lying soils. When digging the hole, do not add fertilizers with the exception of slow-release capsule or premeasured types. Loosen the ropes of a balled and burlapped tree and pull back the burlap from the roots. Leave the burlap in the bottom of the hole where it will quickly decompose.