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Azalea and Rhododendron

Rhododendrons
Rhododendron, Native Rhododendron

Coveted for their spectacular blooms, which come in a wide range of shapes and colors, Azaleas and Rhododendrons are members of the genus Rhododendron, one of the largest genera in the plant world, which includes over 900 species and over 20,000 named hybrids. All are fascinating.

  • These highly popular ornamental shrubs come in all sizes, ranging from dwarf, ground-hugging varieties, which may reach 16 in. in 10 years (40 cm) to giant tree-like specimens as tall as 20 ft. or more (6 m). Both moisture and the length of the growing season will have a serious impact on their growth rate. Some Rhododendrons will experience a fast growth rate (2 ft. per or 60 cm) while others will slowly grow less than 0.5 in. per year (1 cm).
  • Usually blooming in spring for about three weeks, their flowers range from the tiny and delicate blossoms of floriferous dwarf shrubs to the huge ‘trusses’ of tall growing hybrids and species. Some varieties bloom much earlier in the winter, while others blossom in mid to late summer. One big splash of color in spring is great, but what if your garden were to show cheerful colors in winter or late summer? With some planning and plant hunting, you could enjoy these wonderful flowers almost all year long!
  • In bloom or not, many evergreen Rhododendrons feature handsome foliage and make outstanding garden plants year-round.
  • Versatile, these ravishing shrubs can be grown in beds and borders, wall-side borders, city gardens, and cottage gardens. Where space is tight, some cultivars can be grown in patio containers or small gardens. Others are ideal for growing on banks and slopes or as magnificent hedges or privacy screens.

Guide Information

Hardiness 4 - 10
Plant Type Shrubs
Genus Rhododendron
Exposure Partial Sun
Season of Interest Spring (Early, Mid, Late)
Summer (Early, Mid, Late)
Fall
Height 2' - 20'
(60cm - 6.1m)
Spread 3' - 15'
(90cm - 4.6m)
Maintenance Low
Water Needs Average
Soil Type Clay, Loam, Sand
Soil pH Acid
Soil Drainage Moist but Well-Drained
Tolerance Rabbit
Attracts Butterflies, Hummingbirds
Landscaping Ideas Wall-Side Borders, Patio And Containers, Banks And Slopes, Beds And Borders, Hedges And Screens
Garden Styles City and Courtyard, Informal and Cottage, Japanese Garden, Traditional Garden
Rhododendron ‘Blue Tit’
Rhododendron ‘Christmas Cheer’
Rhododendron ‘English Roseum’

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Companion Plants for your Azalea and Rhododendron

  • Shade-loving Hostas are natural companion plants to Rhododendrons and Azaleas. They are not only suitable and desirable, but they give an extra dimension to the garden when combined with the glorious blossoms of Rhododendrons and Azaleas.
  • A variety of charming flower bulbs or perennial plants work well when grown as companion plants to Rhododendrons and Azaleas.
  • Similarly, there are many attractive shrubs that pair beautifully with  Rhododendrons and Azaleas. Among the most popular are Kalmia latifolia (Mountain Laurel) and Pieris japonica (Japanese andromeda) whose particularly attractive blooms overlap with those of Rhododendrons and Azaleas and create a spectacular floral display.
  • There are many other plants suitable for companion planting with your Azaleas and Rhododendrons, so don’t be afraid to experiment and find your own successful plant combinations! These companion plants must however be able to thrive under the same growing conditions as Azaleas and Rhododendrons.
  • Select companion plants that do not compete for moisture with your Rhododendrons and Azaleas or they will suffer – unless you live in a high rainfall area.
Rhododendron ‘Hino Crimson’
Rhododendron calendulaceum (Flame Azalea)
Rhododendron luteum (Pontic Azalea)

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Growing and Caring for your Azalea and Rhododendron

Azaleas and Rhododendrons are not difficult to grow but have special cultural requirements.

  • The soil should be acidic, organic, moist, fertile and well-drained. Each of these conditions is important to grow Azaleas and Rhododendrons successfully. If you have alkaline soil, grow Rhododendrons as container plants since reducing soil pH is not simple. In neutral pH soils, the plants will be unable to get sufficient iron and their leaves will become chlorotic.
    Azaleas and Rhododendrons do not tolerate drought or wet soils (with a few exceptions).
  • Choose a site with dappled shade in sheltered conditions. Avoid deep shade beneath other trees. Dwarf alpine species will tolerate full sun provided the soil is kept evenly moist. Most Rhododendrons will tolerate a more open site if sheltered from cold, dry winds. Plants not given protection from the wind often develop leaf scorch or splitting of the bark on the stems. Avoid frost pockets and sites exposed to early morning sun.
  • Most Azaleas and Rhododendrons are purchased with soil around their roots in containers or “balled”. To plant them properly, dig a hole slightly larger, but no deeper than the container or ball. Set the ball so it is 2 in. higher (5 cm) than the surrounding soil. Never plant Azaleas and Rhododendrons so deeply that their stem is covered deeper than it had been growing in the nursery. Water thoroughly after planting and firm the soil around the ball. There is little need for fertilizing at planting time.
  • Azaleas and Rhododendrons need a heavy mulch to conserve moisture and minimize winter damage. Coarse materials such as partly decomposed oak leaves or pine needles are ideal. Oak shavings, hardwood chips or aged sawdust and sphagnum peatmoss may also be used satisfactorily. Use a mulch of sawdust or hardwood chips about 2 in. deep (5 cm). A mulch of oak leaves should be 4-6 in. deep (10-15 cm). Keep the mulch around the plants all year, but don’t allow it to be too high on the plant stems during the summer and fall. In winter pile it higher to help prevent winter leaf scorch or bark splitting on the stems. A good heavy mulch has also the merit of keeping down weeds.
  • Azaleas and Rhododendrons grow well naturally at fairly low nutrient levels. Therefore, fertilization should be done carefully to avoid their delicate roots to get damaged. A light application of a fertilizer formulated for acid-loving plants may be added to the surface, according to the directions on the package, before the mulch is applied. Fertilizing should be done in the spring and never later than midsummer. Late summer fertilization may force out tender fall growth that will be killed by the winter.
  • Rhododendrons do not require much pruning other than the removal of dead wood and deadheading of spent flowers (if doable).
  • They can be propagated from semi-ripe cuttings grafting or layering.
  • Keep an eye out for vine weevil, rhododendron leafhopper, scale insects, bud blast, azalea gall and honey fungus.
Rhododendron arborescens (Sweet Azalea)
Rhododendron atlanticum (Coastal Azalea)
Rhododendron catawbiense (Catawba Rosebay)

Garden Examples

A Pretty Spring Border Idea with Rhododendrons and Crocuses
A Pretty Spring Border Idea with Rhododendrons and Tulips
A Charming Plant Combination for Shady Gardens: Hydrangea, Japanese Maple and Boxwood
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Rhododendron
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While every effort has been made to describe these plants accurately, please keep in mind that height, bloom time, and color may differ in various climates. The description of these plants has been written based on numerous outside resources.

Guide Information

Hardiness 4 - 10
Plant Type Shrubs
Genus Rhododendron
Exposure Partial Sun
Season of Interest Spring (Early, Mid, Late)
Summer (Early, Mid, Late)
Fall
Height 2' - 20'
(60cm - 6.1m)
Spread 3' - 15'
(90cm - 4.6m)
Maintenance Low
Water Needs Average
Soil Type Clay, Loam, Sand
Soil pH Acid
Soil Drainage Moist but Well-Drained
Tolerance Rabbit
Attracts Butterflies, Hummingbirds
Landscaping Ideas Wall-Side Borders, Patio And Containers, Banks And Slopes, Beds And Borders, Hedges And Screens
Garden Styles City and Courtyard, Informal and Cottage, Japanese Garden, Traditional Garden
Compare All Rhododendron
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Explore Great Plant Combination Ideas
Rhododendron
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Rhododendron

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