[header] How to rescue dying landscape plants [title] Assess your plants' watering needs. [step] Under-watering is a far more common problem than overwatering. As a general rule, each square foot of the landscape needs about 2-3 quarts of water weekly. 
Or, about 20 liters (5.3 us gal) per square meter. Put another way, it needs to receive at least 1 inch (2.5 cm) of rain or water each week.