Rhododendron shrub in full bloom
image by Harald Koster: Commons.wikimedia.org
Rhododendrons and their close relative azaleas are a family of evergreen and deciduous perennial blooming shrubs. Rhododendrons have a dense billowing growth habit and produce a profusion of bloom in the spring. They thrive in sun and partial shade in slightly acidic and nutrient-rich, moist soil. They are relatively low maintenance, requiring little to no pruning and are not a strong attractant to insects and pests.
Select a planting locale for your rhododendron that has a full-sun to partial-shade exposure. Some rhododendron varietals can perform well in heavier shade settings, but most prefer several hours of full sun each day for optimal bloom performance. Also consider the mature height and spread of the shrub when selecting a site, as rhododendrons do not like to be disturbed after they are established in a location. Choose a site that is somewhat protected from heavy winds, which can be drying and cause damage to the shrub in winter.
Plant your rhododendron in the early spring or fall, bypassing the heat and drought stress of summer. Prepare a planting hole in rich, well-drained soil that is at least twice the diameter of the root ball and at least as deep. Till up the surrounding soil well to loosen it and assist the roots in penetrating the new soil. Maintain the identical planting depth in the new soil as the shrub had in its nursery pot or burlap ball.
Place the rhododendron in the hole and turn the shrub until its most pleasing aspect is facing the direction from which it will most often be viewed. Backfill soil around the root ball, packing the soil lightly with your hands or heel and pausing halfway to water in the soil. Finish filling in the soil and create a moat around the drip line of the shrub with the excess soil. Fill the moat with water and allow it to percolate into the soil before filling a second time. Lay down at least a 2-inch deep blanket of mulch, such as shredded bark, leaf mold or compost, or some combination thereof, to keep weeds at bay and prevent moisture loss.
Water your newly planted rhododendrons regularly so that the soil around their roots is consistently moist throughout the growing seasons. Water deeply before the ground freezes in the winter to provide a buffer against winter drought. After the rhododendron is mature and well established, likely after three years in the same location, you will be able to scale back applied irrigation significantly so that you are only watering during drought conditions. Apply a general purpose, water-soluble fertilizer such as Miracid around the root ball and drip line of the shrub in the spring. Always lay down your fertilizer onto wet soil to prevent burn, and water the fertilizer itself in well.