From Ground: Water the warminster broom plant a couple of hours before you plan to move it. This helps to hydrate the plant and makes the soil easier to work with. To remove the plant, hold the base and gently wiggle as you lift to avoid damaging the roots. If the plant is larger, you may need to use a spade to dig around and under the root ball to free it.
From Pot: Water the potted warminster broom well, then tilt the pot to the side and gently pull the plant out. Mainly hold the pot, not the plant, to avoid damaging the stems or leaves.
From Seedling Tray: Gently squeeze the individual cell where the warminster broom seedling is to help get the seedling out without pulling on the stem. Gradually lift it while supporting the root ball. If the plant doesn't slip out easily, use a butter knife or small tool to help it along.