“Does every plant require one inch of water each week?” asked a visitor to the Gloucester Master Gardeners’ booth at the Daffodil Festival. That is a good question, because care instructions for most plants use the “one inch per week” rule of thumb. Many factors affect the amount of water any species will need. Ice plant (Lampranthus spp.), a succulent groundcover that is native to South Africa, grows in full sun and tolerates drought conditions. Lily-of-the-valley (Convallaria majalis) prefers part shade and moist, organically rich soil. If both plants were given one inch of water per week, the ice plant likely would rot and the lily-of-the-valley might dry up. Watering needs depend on several factors, including climate, sunlight, humidity, and proximity to other plants that require more or less water. The Clemson University Extension publication HGIC 1801 “Landscape Irrigation Management Part 2: Determining When to Irrigate” offers two techniques to help you determine when plants nee...