Hi Adam: I apply soil sulfur for the blueberry bushes in the same bed and yes, the soils are alkaline. The soil pH ranges somewhere between 7.2 and 7.8 at Chicago Botanic Garden and the soils at my house were derived from the same environmental factors - probably near the higher end of the spectrum. Rhododendrons, Vaccinium and other Ericaceceae plants all exhibit typical iron chlorosis and foxtailing (magnesium deficiency) if no effort is made to lower the pH. Boyce Tankersley Director of Living Plant Documentation Chicago Botanic Garden 1000 Lake Cook Road Glencoe, IL 60022 tel: 847-835-6841 fax: 847-835-1635 email: firstname.lastname@example.org -----Original Message----- From: email@example.com [mailto:firstname.lastname@example.org] On Behalf Of Adam Fikso Sent: Wednesday, September 01, 2010 11:57 AM To: Pacific Bulb Society Subject: Re: [pbs] Hardy gloxinia Boyce? Why do you top-dress with powdered sulfur? Is your soil alkaline?