Newly planted evergreens should be watered regularly during the first year after planting. They should be soaked by rain or supplemental watering once a week, or more during hot, dry weather on sandy soils. Keep watering right up until the ground freezes. It is important that evergreens are fully hydrated going into winter. Because evergreen foliage is retained through winter, it is exposed to drying winter winds. With frozen ground and roots, plants cannot replenish that moisture and can "burn" or brown by spring.
Most evergreens require well-drained soil, and overwatering them will result in stress and damage to roots. Feel the soil near the shrub about 1-inch deep. If the soil feels dry, thoroughly soak the soil around the root zone. Avoid overwatering - it can be just as harmful as underwatering. Plant roots need oxygen as well as water. Too much water fills the air pockets between soil particles and creates an anaerobic environment. This can result in root rot and an environment favorable to other pathogens such as fungi and bacteria.