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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #213025

Title: Rate of Nitrogen Fertigation during Vegetative Growth and Spray Applications of Urea in the Autumn Alters Growth and Flowering of Florists' Hydrangeas

Author
item BI, GUIHONG
item Scagel, Carolyn
item HARKESS, RICHARD
item PARIDON, KERI

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/11/2007
Publication Date: 4/1/2008
Citation: Bi, G., Scagel, C.F., Harkess, R., Paridon, K. 2008. Rate of nitrogen fertigation during vegetative growth and spray applications of urea in the autumn alters growth and flowering of florists' hydrangeas. HortScience. 43(2):472-477.

Interpretive Summary: Plants of Hydrangea macrophylla 'Merritt's Supreme' were fertigated with different rates of nitrogen (N) from July to September 2005 and sprayed or not with 3% urea in late October to evaluate whether plant N status during vegetative growth influences plant performance during forcing. Increasing N fertigation rate in 2005 increased plant biomass and plant N content. Spray application of urea (urea sprays) in the autumn had no influence on plant biomass but increased plant N content. In general, plants grown with 210 and 280 mg/l N during 2005 had the greatest growth (total plant biomass, height), flowering (flower biomass, number of flowers, flower size), and leaf quality (leaf area and chlorophyll content) during forcing in 2006. Urea sprays prior to cold storage increased plant growth, flowering, and leaf quality characteristics during forcing. Spraying plants with urea in the autumn decreased plant dependance on N applications during forcing. We conclude that both vegetative growth and flowering during forcing of 'Merritt's Supreme' hydrangea are influenced by both the N status prior to forcing and N supply from fertilizer during forcing. A combination of optimum rates of N fertigation during the vegetative stage of production with urea sprays prior to cold storage could be a useful management strategy to control excessive vegetative growth, increase N storage, and optimize growth and flowering of container-grown florists' hydrangeas

Technical Abstract: Plants of Hydrangea macrophylla 'Merritt's Supreme' were fertigated with 0, 70, 140, 210, or 280 mg/l nitrogen (N) from July to September 2005 and sprayed or not with 3% urea in late October to evaluate whether plant N status during vegetative growth influences plant performance during forcing. In late November, plants were manually defoliated, moved into a dark cooler for 8 weeks, and then placed into a greenhouse for forcing. After budbreak, plants were supplied with either no N or 140 mg/l N for 9 weeks. Plant growth and N content were evaluated in November 2005 prior to cold storage and plant growth, flowering, and leaf quality parameters were evaluated in late April 2006. Increasing N fertigation rate in 2005 increased plant biomass by ~14g, and plant N content by ~616mg. Spray application of urea (urea sprays) in the autumn had no influence on plant biomass but increased plant N content by ~520 mg. In general, plants grown with 210 and 280 mg/l N during 2005 had the greatest growth, flowering, and leaf quality during forcing in 2006. Urea sprays prior to cold storage increased plant growth, flowering, and leaf quality characteristics during forcing. Increases in N content during 2005 were positively related to plant growth and flowering during forcing. Providing plants with N during the forcing period also improved plant growth, flowering and leaf quality characteristics. Urea sprays in the autumn were as effective as N fertilizer in the spring on improving growth and flowering. We conclude that both vegetative growth and flowering during forcing of 'Merritt's Supreme' hydrangea are influenced by both the N status prior to forcing and N supply from fertilizer during forcing. A combination of optimum rates of N fertigation during the vegetative stage of production with urea sprays prior to cold storage could be a useful management strategy to control excessive vegetative growth, increase N storage, and optimize growth and flowering of container-grown florists' hydrangeas.