Re: JI Fertilizer Conflict (Soil pH)
- Subject: Re: JI Fertilizer Conflict (Soil pH)
- From: r*@dmv.com
- Date: Sun, 08 Oct 2000 08:27:52 -0400
> There is a question that has me puzzled. Authorities typically warn iris
> gardeners that lime and/or Calcium are fatal to Japanese Iris (JI).
> These same authorities also recommend the use of Rhododendron and Azalea
> fertilizers, superphosphate, and other general purpose or flower
> fertilizers when fertilizing Japanese Iris.
Dallas,
I don't see the conflict. Very few, if any conventional fertilizers
effectively raise soil pH and high nitrogen fertilizers (recommended for
JI's) actually lower soil pH. Logically, if fertilizers raised pH, there
would be no need for farmers to apply lime (by the ton) in addition to
fertilizer.
I've never seen a recommendation for use of superphosphate on JI's. They
are described as "heavy feeders", but that generally refers to nitrogen.
The availability of phosphate in the soil is pH dependent, with optimal
availability around pH 6.5 and perhaps higher. Since JI's need a lower
pH, phosphate that is added to the soil mix wouldn't be available
anyway.
R. Dennis Hager
on Delmarva
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