Use of Precharged Zeolite to Provide Aluminum During Blue Hydrangea Production

Abstract

Aluminum (Al) drenches are repeatedly applied during blue hydrangea (Hydrangea macrophylla Thunb.) production because Al is required for blue sepal coloration, but soilless root media do not retain Al. The ability of clinoptilolitic zeolite to retain and release Al, and its evaluation as the sole source of Al during blue hydrangea production, was evaluated in laboratory and greenhouse experiments. Adsorption and desorption isotherms indicated that Al is adsorbed and released by this zeolite. Clinoptilolite was precharged with Al and combined at 10–40% with a peat and perlite mix to evaluate its use as a sole source of Al during the production of mini‐pot blue hydrangea “Kuhnert.” Root medium Al, pH, and electrical conductivity (EC) were measured during production. Sepal color and growth measurements, and foliar and sepal analyses were conducted at the end of the production cycle. Aluminum from zeolite was released rapidly during the vegetative stage of production. Dry mass of plants grown with 10 and 20% zeolite was similar to the commercial control. Blue sepals were produced in the 10–40% zeolite treatments, however, growth was significantly reduced from the 30 and 40% zeolite treatments. Aluminum‐charged zeolite up to 20% of the root medium may be used as a sole source of Al during forcing and may simplify blue hydrangea production; however, its use affects phosphorus (P), potassium (K), pH, and EC management.