The Magnesium Question
Ann Marie Harris
ARS Master Consulting Rosarian, Reno Rose Society

I have always been told - and have told all of you - to add magnesium in the form of Epsom Salt as part of a fertilizing program in spring and mid-summer to promote basal breaks. Since I was told to do so by local and national experts, I never questioned whether this was necessary. In the May issue of The Rose Parade, Jan Weverka explained why, in some geographic areas, this practice may not only be an extra expense but a waste of time.

Apparently, if your local water supply contains at least 15 parts per million (ppm) magnesium, you are providing enough magnesium to your roses by simply applying water. Jan thought the wide-spread touting of Epsom Salt might have originated in the Sacramento area where there is a deficiency of magnesium in the soil. Jan said that southern California heard about the great results from Epsom Salt and began using it also.

Spring water in the eastern Sierra Nevada near our area has less than 2 ppm magnesium. According to Westpac Utilities/Sierra Pacific, which supplies most of the water in the Reno-Sparks area, the magnesium content of our water varies a lot. Water from the Truckee has around 4 ppm to 20 ppm. As water delivered to homes in the Truckee Meadows is usually 80-85% river water, bottom line on magnesium is add Epsom Salt!

Members living in the Carson Valley, Carson City area, Fallon, or Washoe Valley probably have similar magnesium contents in water used at their homes. Best bet is to add Epson Salt. Call your local water provider if you really want to find out the magnesium content. If you are using a private well and want to find out, you will need to send a sample in to a laboratory for analysis. This usually costs money. Your local cooperative extension may have some general figures for your area.

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