I have a few plants around the garden that really look awful. The foliage is very yellow. These include the "Just Like Picasso" Petunia in a hanging basket, Starfighter Lily in ground for 3 years, Charles Albanel Explorer Rose. I have applied iron, added gypsum and fertilizer regularly. The problem is the PH of the soil. All of the problem plants are growing in a soil PH of 7.3 or higher. I need to get the PH lower (more acidic) to 6.5 or so (try for less than 7.0). I'm going to apply aluminum sulphate to the problem areas. I am also going to try to use rain water for the containers with petunias as much as possible since our tap water is quite alkaline.
Has anyone dealt with this and/or have some comments/suggestions.
Here's a picture of the rose, which is near a old concrete driveway. I have been told that the concrete will leech over years and will be a factor in the soil PH (alkaline or higher PH). The info in the soil tester states the the high alkaline soil inhibits the plant to uptake nutrients. Guess that would be a big part with the petunia