Watering the Kousa dogwood helps transport the needed nutrients from the soil to the rest of the plant. The moisture will keep this species healthy if you know how much water to give. The watering requirements will depend on the weather in your area and the plant's soil. The Kousa dogwood thrives on moist soil, but they can't generally tolerate waterlogging. Ensure to provide enough mulch when planted on the ground and never fall into the trap of watering too little. They enjoy a full can of watering where the water should be moist at the base when they are planted in a pot to get the best blooms. If they are grown as foliage, you need to water them up to a depth of 10 to 20 inches so they will continue to grow. If it's raining, refrain from watering and let them get the nutrients they need from the rainwater.