Rhododendron care, combined with the knowledge of knowing what to do, will help you grow beautiful thriving rhododendrons. This article will give you some general and specific information on rhododendron care to help you grow them with as little effort as possible. They make excellent landscape plants and add color to any canvas or canopy gazebo in your yard or garden.
Rhododendrons and azaleas are noted for their gorgeous and abundant spring blooms. Bloom time can be long in a cool, humid spring. Summer foliage is not particularly attractive on deciduous azaleas, but evergreen types have attractive green leaves.
These plants are in the genus Rhododendron but are generally separated into rhododendrons or azaleas based on their leaf and flower type. In general, azaleas are deciduous and rhododendrons are evergreen.
Rhododendron flowers resemble bells; while azaleas blossoms are more funnel shaped. They both make excellent specimen plants and are good for massing on larger sites. Evergreen types can be used in foundation plantings. In cold climates deciduous types grow well in full sun or partial shade. In the South both types need shade. They need well-drained, acid soil. Acidify the soil before planting. Do not plant them in poorly drained soil, near salt spray, in high pH soil, or on exposed sites with winter sun and wind.
If Rhododendrons are planted in containers or if they are balled-and-burlaped, should be transplanted in spring. Plants show iron chlorosis (yellow leaves) if the soil is too alkaline. Mulch with pine needles, shredded pine bark, or compost to keep the shallow roots cool and moist and the soil acid. Feed the plants every spring with acid-based fertilizer such as Miracle-Gro Shake ‘n Feed Azalea, Camellia, Rhododendron. You should maintain an even supply of moisture throughout the growing season. Prune after flowering if necessary.
Propagation of rhododendrons is done by taking hardwood cuttings in midsummer. Layer them in summer right after they flower. The seeds should be sown indoors in the winter.
Pests and Diseases that you may find on rhododendrons are usually in the form of root rot, which is a problem in poorly drained soils; powdery mildew can also be a problem in humid weather. Canker and leafspot are also common diseases found on rhododendrons. Pests include Lacebugs, Japanese beetle and spider mites.
Quick Facts on Rhododendron Care:
- Zones- 4-10
- Size- 1-20’h x 1-20 w
- Type- Evergreen or deciduous shrub
- Form- Upright to spreading
- Texture- Medium to coarse
- Growth- Slow
- Light- Shade to Sun
- Moisture- Medium to high
- Soil- Acid, well drained
- Features- Showy spring flowers
- Uses- Shrub border, groupings, massing
Rhododendron Care Tips:
- Pinch new growth to promote branching
- Remove spent flower clusters to keep plants neat
- Water plants during dry periods to help reduce leaf scorch and winter injury
- Winterize your evergreens
Other Related Species of Rhododendrons
Carolina rhododendron (R. Carolinianum) is an evergreen that is hardy in zones 5-8; it grows 3-6’ in height. The flowers range from pure white to rose to lilac-rose and appear in mid-to late spring.
Catawba rhododendron (R. Catawbiense) is an evergreen reliably hardly in zones 5-8 but can be grown in protected sites in zone 4. It grows 6-10’ in height and has good evergreen foliage. Catawba Flowers are lilac-purple with green or yellow-brown markings inside and appear in mid to late spring. Although ‘Roseum Elegans’ has beautiful showy pink flowers.
Korean rhododendron (r. Mucronulatum) is reliably hardy in zones 5-8 but can be grown in protected sites in zone 4. It grows 4-8’ tall. This group is a good choice for landscape use. The rosy-purple flowers are among the first of the species rhododenrons to appear in spring.
P.J.M rhododendrons hybrids are among the hardiest rhododendrons- to zone 4. They have lavender-pink flowers.
Other Hybrid Groups of Azaleas
Gable hybrids are small-leaved evergreens hardy in zones 6-8. Their flowers are generally red to purple. Ghent azaleas are deciduous with single or double flowers. The Lights Series are the hardiest azaleas, all surviving in zone 4 and some in zone 3. The colors range from lemon yellow to lilac.
Miracle-Gro Plant Food for Azaleas, Camellias, and Rhododendrons, 1.5-Pound (Fertilizer for Acid Loving Plants)