Perennials need summer watering, preferably infrequent deep waterings. Apply an inch of water each week, or as needed, depending on soil type.
Start watering in mid-morning, water through mid day, ending early enough so plants dry off before evening. Temperatures in the 90's may prohibit daytime watering. Evening watering gives wet leaves with cool night temperatures making disease development easier. Avoid light sprinklings with a hand held hose every evening.