> one part was a little too steep and dry, the TB didnt do well there, and
> the soil there
> was pretty sour. How sour soil can a TB take? what is the ideal PH?
It is usually considered that a neutral pH (7.0) is ideal for TB iris,
although they have a fairly wide tolerance. However, TB performance is
almost sure to suffer in really sour (acid) soils. How low does the pH need
to be before there is a noticeable effect 5.5? 5.0? Lower?
The combination of dry and sour soil is a difficult one for gardening, as
most plants, including iris, that have preferences either prefer moist and
acid or drier and neutral-to-alkaline conditions, as these are the
combinations most widely found in nature.
Jeff Walters in northern Utah (USDA Zone 4, Sunset Zone 2)