From Ground: Begin by watering the knobby club-rush plant to dampen the soil. This will make extraction easier and less damaging to the root system. Using a spade or shovel, carefully dig a wide trench around the plant ensuring the plant's root ball remains intact. Work the spade or gardening fork under the root ball and gently lift the plant from its original location.
From Pot: Water the plant and let it absorb the water for a while. After that, gently tip the pot sideways and slide the knobby club-rush out, taking care not to damage the foliage or roots. If the plant is root-bound, you may need a bit more force to remove it, but do so carefully.
From Seedling Tray: Water the seedlings well so that you can remove them with substantial soil clinging to the roots. Use a hand trowel or a spoon to scoop out individual knobby club-rush seedlings to avoid causing damage.