and August heat can stress them fast. I try to give established plants the equivalent of 1 to 1.5 inches of water per week, including rainfall. In practical terms, that usually means a slow, deep soak once or twice a week instead of a quick sprinkle every evening. A mature vine often needs about 2 to 4 gallons at a watering, depending on soil type and size.
If your soil is sandy, you may need to water every 3 to 4 days during a stretch of 90-degree weather. In