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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #305559
Title: Irrigation frequency during container production alters rhododendron growth, nutrient uptake, and flowering after transplanting into a landscape

Author
item Scagel, Carolyn
item BI, GUIHONG - Mississippi State University
item Bryla, David
item FUCHIGAMI, LESLIE - Oregon State University
item REGAN, RICHARD - Oregon State University

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2014
Publication Date: 7/1/2014
Citation: Scagel, C.F., Bi, G., Bryla, D.R., Fuchigami, L.H., Regan, R.P. 2014. Irrigation frequency during container production alters rhododendron growth, nutrient uptake, and flowering after transplanting into a landscape. HortScience. 49(7):955-960.

Interpretive Summary: One deciduous cultivar of Rhododendron L., ‘Gibraltar’ (AZ), and two evergreen cultivars, ‘P.J.M. Compact’ (PJM) and ‘English Roseum’ (ER), were grown in containers for 1 year to determine the effects of irrigation frequency during container production on plant performance the following spring when the plants were transplanted into the landscape. Three months after transplanting into the landscape, nutrient uptake, growth, and flowering were evaluated. In general the effects of irrigation frequency in containers on performance in the landscape differed between the deciduous cultivar and the evergreen cultivars. In AZ, less frequent irrigation in containers had a pre-conditioning effect that resulted in greater vegetative growth in the landscape but less reproductive growth. In contrast, less frequent irrigation reduced vegetative growth of evergreen cultivars in the landscape and improved flowering. In the deciduous cultivar, less frequent irrigation increased nutrient reserves and improved the ability of the plants to absorb and utilize nutrients after transplanting, but in the evergreen cultivars, it generally decreased nutrient uptake after transplanting. Less frequent irrigation also altered plant attributes that are important to consumers, including developing a sparser canopy in ER and a fuller canopy in PJM, and producing more but smaller inflorescences in both cultivars. Our results indicate that irrigation frequency during container production of Rhododendron results in a trade-off between vegetative and reproductive growth the following spring when the plants are in the landscape.

Technical Abstract: One deciduous cultivar of Rhododendron L., ‘Gibraltar’ (AZ), and two evergreen cultivars, ‘P.J.M. Compact’ (PJM) and ‘English Roseum’ (ER), were grown in containers for 1 year to determine the effects of irrigation frequency during container production on plant performance the following spring when the plants were transplanted into the landscape. Three months after transplanting into the landscape, nutrient uptake, growth, and flowering were evaluated. In general, the effects of irrigation frequency in containers on performance in the landscape differed between the deciduous cultivar and the evergreen cultivars. In AZ, less frequent irrigation in containers had a pre-conditioning effect that resulted in greater vegetative growth in the landscape but less reproductive growth. In contrast, less frequent irrigation reduced vegetative growth of evergreen cultivars in the landscape and improved flowering. Different growth responses to irrigation frequency between deciduous and evergreen cultivars appeared to be related to differences in timing of nutrient uptake and mobilization. In the deciduous cultivar, less frequent irrigation increased nutrient reserves and improved the ability of the plants to absorb and utilize nutrients after transplanting, but in the evergreen cultivars, it generally decreased nutrient uptake after transplanting. Less frequent irrigation also altered plant attributes that are important to consumers, including developing a sparser canopy in ER and a fuller canopy in PJM, and producing more but smaller inflorescences in both cultivars. Landscape performance was related to plant nutrition in containers; however, irrigation frequency in containers disrupted relationships between nutrition and performance in all three cultivars. Our results indicate that irrigation frequency during container production of Rhododendron results in a trade-off between vegetative and reproductive growth the following spring when the plants are in the landscape.