If plants are somewhat pot-bound at planting time, loosen the roots around the bottom and sides of the root ball and spread them out in the bottom of the planting hole. To encourage side root growth, make the hole twice as wide as deep. Refill the hole, firming the soil in around the plant to avoid air pockets. Watering Water plants thoroughly following planting to settle the soil around the roots. Pay especially close attention to watering the first few weeks while plants develop their root systems.
Adequate moisture is essential for the growth of perennials.
Most perennials require at least 1 to 1 inches of water per week from rain or irrigation. More may be needed during very hot weather. To promote deep root growth, water thoroughly and deeply. Allow the soil surface to dry before watering again. Soaker hoses and drip irrigation are ideal watering methods since they save water and avoid wetting leaves and flowers.