Dormant budded plants of Hydrangea macrophylla (Thunb.) cvs. Blaumeise Blue and Pink were planted on 29 Jan. 1996 in 15-cm azaleas pots containing media with topsoil, peat, perlite, coal bottom ash, and mine soil, mixed in varying proportions. Media pH levels were initially adjusted with dolomitic limestone to a range of 6.0 to 6.1 for pink inflorescences and with ammonium sulfate to a range of 4.4 to 5.9 for blue inflorescences. Plants of Blaumeise Blue and Blaumeise Pink in low pH media were drenched on 29 Feb. with a solution of aluminum sulfate at 6 g·L–1. Number of shoots per plant were reduced in media with the highest proportion of coal bottom ash (40%, v/v) plus 30% mine soil. Plant diameter was affected very little by type of media. Tallest plants were `Blaumeise Pink' growing in media containing at least 20% top soil or mine soil plus 20% coal bottom ash. These mixes also contained 20% or 40% perlite. Inflorescence diameters ranged from 10.88 to 17.43 cm. and were mostly unaffected by media type. Inflorescence number per plant appeared to be reduced in `Blaumeise Blue' regardless of media. Inflorescence color brightness ranged from L = 55.26 to 61.38 and was affected very little by media type in both cultivars. Bluest inflorescences occurred on `Blaumeise Blue' plants growing in a combination of zero top soil, 40% peat, 30% perlite, 20% coal bottom ash, and 10% mine soil with no lime, and`Blaumeise Pink' plants growing in media with zero topsoil, 40% peat, and 20% mine soil. Blue color did not develop well in media containing top soil and no mine soil. This study demonstrated that florists' hydrangea can be satisfactorily forced in media containing substantial amounts of coal bottom ash and mine soil and that color regulation is also possible in some of these media.
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