I’ve been suspecting for the last few years that a large problem for our garden and orchard is our hard water. Once I start introducing water from our irrigation, after the spring rains have dried up, the leaves curl, get bumpy, and often develop a white spotty film on their exterior, like a mineral buildup or something.
Is the water the cause of these symptoms in my plants?
As suggested, your water may be the cause of the white spots. You'll need to check with your water supplier to determine how hard your water is. If you are using well water, you would need to have the water tested to determine this. I don't think hard water would cause the leaves to curl or get bumpy, so those symptoms may be a different issue.
Water classification
General guidelines for the classification of waters are:
- 0 to 60 mg/L of calcium carbonate is classified as soft
- 61 to 120 mg/L of calcium carbonate is moderately hard
- 121 to 180 mg/L of calcium carbonate is hard
- 180+ mg/L of calcium carbonate is very hard.
Causes of white spots on leaves
Other possible causes of the white spots would be a fungus (e.g. powdery mildew), insect (e.g. scale), or pesticide residues. From this specific photo, it doesn't look like a fungus or insect. Sometimes when plants transpire, they can leave behind white salt residues on the leaves, so that also may be the cause.
The following resources have more information on these potential causes:
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