From Ground: First, water the california blackberry plant to make the soil damp, not sopping wet. This will make it easier to remove. Next, dig around the plant with a wide berth to protect the root ball, using your shovel or trowel. Keep the root ball intact as much as possible and gently remove the plant from the ground. Larger plants might require more effort to lift.
From Pot: Start by
watering the potted california blackberry plant. Tip the pot on its side and gently ease the plant out, again, keeping the root ball intact. If the plant resists being removed, tap the sides and bottom of the pot to loosen it.
From Seedling Tray: Water the california blackberry seedlings until the soil is quite damp. Carefully grip the upper part of the plant's main stem with one hand. With the other hand, push up on the bottom of the seedling tray pocket to remove the plant.