Root Growth and Water Status of Container-grown Photinia ×fraiseri Dress Transplanted into a Landscape

Photinia plants produced in 11.4-liter polyethylene containers using a pine bark-based medium were transplanted into a well-drained sand and irrigated on alternate days. Polyethylene barriers were placed under half the root balls at transplanting to limit gravitational water loss. Plant water potential was measured diurnally between irrigations, and root growth was determined at 4-month intervals. Plants with barriers averaged higher cumulative daily water stress than control plants over the year, although predawn and minimum water potentials were similar. Growth index and trunk diameter were similar for the plants over barriers and controls, but the former were taller after 1 year. Plants with barriers had twice the horizontal root growth into the landscape site as control plants, resulting in twice the root mass in the landscape after 1 year.