Irrigation causes hydrangea leaf spots

Q: My hydrangea bushes looked great earlier this summer, then we left for a couple of vacations. The irrigation system was set to spray twice a week and ½ inch of water applied at a time. We came home and there were purple spots all over the bushes.

A: My observation is that the discolored leaves and disease spots are concentrated on the upper part of the shrub. It is very likely this was caused by irrigation water keeping the humidity high around the leaves….which led to disease.

Once they are established, hydrangeas rarely need watering. Redesign your irrigation so that water does not hit the leaves. You could use drip irrigation on the roots if the shrubs need water during a severe drought.

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