From Ground: Start by
watering the staghorn sumac plant to soften the soil. With a shovel, dig a circle around the plant wide enough to include all the roots. Be careful not to damage the root ball. Once done, carefully work the spade under the root ball and gently lift the plant from the ground.
From Pot: Water the soil in the pot until it's moist. Turn the pot sideways, hold the staghorn sumac close to base, and gently tap the edge of the pot against a hard surface. This allows the whole plant- root, soil, and all to slide out. If the plant is root-bound, you may need to squeeze or crack flexible plastic pots to loosen the root ball.
From Seedling Tray: Moisten the soil before removing the staghorn sumac to prevent root injury. Handle the plant by the root ball, not the stem or leaves, as you remove it from the tray. If stuck, tap the bottom of the tray to loosen the plant.