Answer: If you have a choice, apply water only to the soil. Water that remains on the foliage for long periods of time (especially overnight) can encourage fungal diseases. Water splashing on the foliage can also spread disease problems. So, try to keep water off the foliage of your annuals and perennials and they will be healthier.
Just to confuse the matter, both broadleaf and needled evergreen shrubs can benefit from an occasional shower with a hose. Rinsing shrubs off during the summer months can rinse off dust and deter spidermites (they love hot, dusty situations).
Best wishes with your garden!
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