Container Type Affects Irrigation Requirement of Viburnum trilobum 'Compactum'

It is commonly believed that growing nursery crops in fabric containers requires greater irrigation inputs. This is based on the assumption that porous sidewalls of fabric containers display more rapid evaporative water loss rate than the industry standard container (black plastic; BP). Research conducted at Colorado State University (Fort Collins, Colo.) examined evaporative water loss from containers using gravimetric and volumetric soil moisture measurements. The three container types (BP, Root Pouch® (RP) and Smart Pot® (SP)) were initially examined in a greenhouse setting. We found that the fabric containers (RP and SP) lost water more rapidly compared to BP containers. In a second study, plastic-wrapped RP and SP containers behaved similarly to BP containers, suggesting that there is significant water loss through the sidewalls of fabric containers. A third study, conducted outdoors using Viburnum trilobum ‘Compactum’, examined plant growth and quality under varying levels of deficit irrigation (25, 50 and 75% of potential evapotranspiration (ET)). Plants grown in BP containers had significantly greater cumulative ET rates (4700 mL), compared to plants grown in RP (3900 mL) and SP (4200 mL) containers. Plants grown in BP containers displayed delayed wilting and scorching of leaves compared to RP- and SP-grown plants. Following a 16-day dry-down, where no supplemental irrigation was provided, plants grown in BP containers displayed the least amount of drought stress compared to RP and SP. We conclude that plants growing in fabric containers under deficit irrigation exhibit more rapid water loss and earlier symptoms of drought stress than plants growing in BP containers. However, when all containers were irrigated at 100% ET, there were no water use or growth differences among container types.