Multiple species of ivy (Hedera spp.) are evergreen plants prized for their attractive, sometimes variegated foliage and a spreading, vining or climbing habit, depending on the type of support provided. The well-known and widely available English ivy (Hedera helix) survives outdoors year-round in U.S. Department of Agriculture plant hardiness zones 5 through 9. When an ivy growing in a pot looks crowded and its growth has slowed, the growing medium dries out almost immediately following watering, or you observe roots growing out of the container's drain holes or above the soil surface, the ivy would likely benefit from transplanting into a larger container, or division and replanting of a smaller section of ivy back into the original container.
Put on gloves before handling the ivy plant to avoid letting the plant sap from coming into contact with your skin.
Water the ivy in its current container well a few hours to a day before you transplant it to make the soil and root mass easier to work with and minimize stress to the plant.
Place a few inches of well-drained, high-quality potting soil in the bottom of a clean container about 1 to 2 inches larger than the ivy's current pot. Any container should offer plenty of holes for drainage. Alternatively, dig a hole two to three times wider than the ivy container and as deep as the container in the spot where you want to plant the ivy outdoors.
Slide the ivy's root mass out if its current container by positioning the plant on its side or upside down, and cradling the soil surface and plant with one hand while removing the container with your other hand.
Inspect the root mass. Use a sharp knife to cut off any dead, brown or mushy roots, leaving only healthy roots, which are firm and white, remaining. For pot-bound plants, with roots that are growing in tight circles around the circumference of the root mass, make four vertical, evenly spaced, inch-deep cuts around the root mass and cut an "X" into the bottom of the ivy's root mass. If you are reusing the same container and want to divide the ivy into multiple, smaller plants to replant separately, use the sharp knife to halve or quarter the root mass, making sure each section created has a proportionate amount of stems.
Set the scored or divided root mass so it is centered atop the soil in the prepared container or planting hole, and fan loose roots out evenly. Add or remove soil under the roots to adjust the planting depth; the ivy should be at the same depth it was previously growing at, with the soil surface about 1 inch below the lip of the pot.
Fill in the space around the root mass with potting soil or soil you removed to dig the planting hole. Gently firm the soil down as you add it to force out major air pockets. Add enough soil so that the ivy is planted at the same depth it was previously growing at, with the new soil level with the plant's existing soil line.
Water the soil around the root mass slowly and deeply, stopping only when the water begins to exit out of the container's drain holes. Add more soil if the existing soil settled when you watered it.