Transplanting a mature Anthony Waterer Spirea


I live in North York. The Anthony Spirea is currently in mostly shade and I want to transplant it to a spot that is about half shade and sun. I want to do that now in June 2020. What should I do to prepare the soil to help it survive in this new spot. Thanks Lorrie


‘Anthony Waterer’ spirea is a cultivar of Japanese spirea (Spiraea japonica ‘Anthony Waterer’). It has a fairly dense, compact habit with showy small red-pink flowers that grow in clusters. Anthony Waterer will perform best in full sun but will tolerate partial shade. It is fairly tolerant of a range of soil conditions but will do best in rich loamy soil.

June is not the best time to transplant established perennial shrubs. The optimal time to transplant is in late fall or early spring when the plant is dormant. There are a few steps you should follow to ensure the best possible outcome when transplanting an established specimen.

Ideally, you should root prune the plant in early spring in preparation for a fall transplant, or in late fall for an early spring transplant. Root pruning involves severing the roots in a circle around the tree in order to prepare a manageable root structure or root ball to dig up and move. Root pruning will allow the plant to grow a stronger root system within the confined area to be dug up. Root pruning should be done after leaf fall or before bud break. Root pruning at other times of the year may weaken the root system and lead to transplant shock.

A shrub 3 feet tall should have a root ball diameter of around 14 inches and a depth of about 11 inches. Dig a trench to the appropriate depth just outside the required diameter of the root ball, separating the topsoil and subsoil into piles so it can be replaced in the right layers.  After backfilling the trench, water the disturbed area to remove air pockets and ensure the roots have enough water.

A root ball with soil can be extremely heavy, so to make moving easier, smaller shrubs under about three feet in height can be bare root planted. Bare root planting involves gently rinsing off some of the soil from the root ball after it has been dug up. Otherwise you can keep the entire root ball intact for the move.

Preparation of the hole in the new location will depend on whether the plant was bare rooted or moved with a root ball. Before digging up the plant, mark the existing soil line around the trunk with tape. For a bare root plant, dig a hole that is 50% wider than the root system. Again, separate the top and sub soil into separate piles. Leave a mound of soil in the middle so the plant is supported and the soil line mark about 1 inch above soil line in the new location. This will allow it to settle slightly over time, so the base of the plant is at the soil line in the new location. Keeping the plant supported, place the plant on the mound and gently spread the roots around the plant in the new hole. Roots should not be allowed to circle around at the edge of the hole. Gently replace the subsoil around the roots, firming into place with your fingers. Water to settle the soil and remove air pockets, and then add the remaining topsoil to the soil line. Gently tamp the soil and water again to settle.

For transplanting with a root ball, dig a hole to the depth of the root ball (again lining the marked soil line with the new soil line) and 50% wider than the root ball, keeping the topsoil and subsoil separate. Replace the subsoil around the root ball firming gently with your fingers, water to settle and then fill to soil line with the remaining topsoil. Again water to settle and firm up gently. There is no need to amend the soil before adding your shrub, but you may want to top dress with compost. Mulch around the base of the shrub to help retain moisture. Ensure the soil around the shrub remains moist (but not saturated) until the roots are fully established.

Further details on these steps and dimensions for root pruning, root balls and soil depth can be found here.