From Ground: Start by watering the rockcress plant to make removing it easier, as moist soil clings less to the roots. With a spade or shovel, dig a wide circle around the rockcress to preserve as much of the root system as possible. Gently maneuver the tool under the plant, and carefully lift the rockcress out of the soil.
From Pot: Water the rockcress thoroughly. Turn the pot sideways, tap the bottom or sides to loosen the root ball, or run a knife around the inside if the plant is stickily rooted. Gently pull the rockcress out by the base of the main stem or by overturning the pot.
From Seedling Tray: Moisten the soil before attempting to remove the rockcress. Use a garden trowel or fork to gently lift the rockcress out of its compartment, ensuring you support the root ball to prevent it from breaking apart.