General
Rhododendrons are evergreen or deciduous shrubs valued for their spectacular spring flowering and lush foliage. They originate mainly from forested mountain regions of Asia and thrive in cool, humid conditions with acidic soils. Growth rate is generally slow to moderate, and many varieties become long-lived landscape shrubs when planted correctly. Because of their shallow root systems, rhododendrons are especially sensitive to drought, soil compaction, and incorrect planting depth.
Light
Partial shade to light shade; tolerates morning sun but prefers protection from strong midday sun.
Soil type
Loose, humus-rich, well-drained acidic soil with high organic content.
Water requirement
Medium to high; soil should remain evenly moist but never waterlogged.
Nutrient requirement
Low to medium; sensitive to over-fertilization.
Precultivation
Rhododendrons are rarely grown from seed by home gardeners due to slow development and variability. Seed propagation requires surface-sowing on sterile, acidic medium, constant humidity, and light for germination, followed by a long juvenile phase. Most gardeners use nursery-grown container plants or cuttings to ensure predictable flowering and growth.
Planting
Plant rhododendrons in spring or early autumn when temperatures are mild and soil moisture is reliable. Choose a sheltered spot with dappled shade and protection from drying winds. Dig a wide but shallow planting hole and amend soil with peat-free acidic compost or leaf mold. The root ball should sit slightly above surrounding soil to prevent waterlogging. Water thoroughly after planting and apply a thick mulch layer.
Pruning
Rhododendrons generally require minimal pruning. Remove faded flower trusses by hand shortly after blooming to prevent seed formation and encourage bud development for the next year. Dead, damaged, or crossing branches can be removed at the same time. Rejuvenation pruning is possible but should be done gradually over several seasons.
Maintenance
Maintain consistent soil moisture, especially during dry periods and winter when evergreen leaves continue to transpire. Use rainwater if possible, as tap water may be alkaline. Fertilize sparingly with slow-release fertilizer for acid-loving plants in spring. Mulch annually to conserve moisture, protect roots, and maintain soil acidity. Avoid disturbing the soil around the plant.
Harvest
Not applicable, as rhododendron is an ornamental shrub grown for its flowers and foliage rather than harvest.
Common issues
Yellowing leaves often indicate iron deficiency caused by high soil pH. Bud drop can result from drought stress or late frost. Root rot may occur in poorly drained soils. Leaf scorch can appear in winter or early spring due to sun and wind combined with frozen ground.
Pollination
Insect-pollinated, mainly by bees and bumblebees.
Companion plants
Azalea, heather (Erica), hydrangea, ferns, hosta.
Incompatible plants
Plants preferring alkaline soil such as lavender, clematis, and many Mediterranean herbs.
