Tuesday, March 30, 2010

Azaleas - Evergreen Species

All Azaleas actually belong to the greater Rhododendron genus of the Ericaceae family

Azaleas - Evergreen

All Azaleas fall into the Rhododendron family!
Azalea bushes thrive under the partial, filtered shade of pine, hickory and Oak, along with companion dogwood trees and camellia shrubs. Azalea plants prefer grown in partial shade, and when planted next to buildings, the north side offers protection from cold damage. The flowers of the azalea plant last longer in filtered pine tree shade because of the cooling effect. Pine tree straw, pine cones, and pine tree bark make excellent mulch under azaleas because it both cools and acidifies the soil. When planting azalea bushes, the shrub should be put into a landscaped hole containing 1/2 soil & 1/2 organic matter, such as peat moss, leaf gro or pine bark. Azalea plants are very shallow rooted and do not do well in compacted or heavy clay soils.

Azaleas love acidic soils, and a pH of 4.5 to 5.5 is perfect for vigorous growth. Watering may be essential if significant rainfall does not occur over two week period and fertilizing is usually not recommended. Fertilizer can burn the tender fibrous roots and may even kill the plant. If yellowing occurs in the leaves or leaf veins, Iron or Magnesium (Epsom salts) can correct the situation. NEVER put lime on an Azalea plant, not only is it wasting money, it can kill the plant.
Healthy Azaleas have bright green glossy leaves in the summer. If the leaves are dull green above and reddening below, that may signal phosphorous deficiency. It is ok to put a water soluble phosphorous fertilizer on the plant but AVOID NITROGEN!
Pruning should be done immediately after blooming to ensure good bloom the following season.
Azalea shrubs are propagated easily by taking a cutting about 8 inches long and placing the cut end about 2 inches deep in sand. These cuttings may root within a week during June and July, and the plant may grow another foot tall before being ready to be planted permanently.







Azalea indicum ( Japanese Evergreen Azalea )
A rapid growing, dense, bushy, medium-size evergreen shrub, native to southern Japan.
Some records include: 10 years - 10 x 8 feet; largest on record - 10 x 10 feet. It is very popular and has been grown for over 300 years.
The leaves, up to 2.3 inches, are brownish and bristly at first, turning to glossy deep green.
The abundant, rosey-red to scarlet-red, broad funnel-shaped flowers, up to 2.5 inches in length, are borne in pairs or singly during late spring into early summer.
Hardy zones 5 to 9

* historic archive photo


'Balsaminiflorum'
A low, mounding, dense, dwarf form only reaching up to 3.3 feet in 10 years ( rarely more ).
The abundant, double, pinkish-red flowers, up to 1.5 inches across, are borne during early summer.
Hardy zones 7 to 9, tolerating as low as -10 F.

'Macrantha'
A compact shrub with larger leaves, up to 2 inches in length. The glossy leaves turn reddish during winter.
The large, pink flowers, up to 2.5 inches in length, are borne during early summer.
Compact in habit, it can reach up to 3.3 feet in 10 years, and an eventual maximum height of 8 feet.

Rhododendron kiusianum ( Kyushu Azalea )
A low dense evergreen shrub, typically reaching no more than 3 x 5 feet, and is native to island of Kyushu in Japan.
Some records include: 10 years - 2 x 3 feet; largest on record - 8 x 6 feet. It is one of the parents of the Karume Azaleas.
The obovate leaves, up to 1.6 x 0.5 inches, are green.
The intense purplish-pink, funnel-shaped flowers, up to 2 inch in length, are borne in trusses of 2 to 3 during
Hardy zones 5 to 9 ( tolerating -20 F ). One strain is known to have survived -38 F. In cold climates, it may become deciduous.

* historic archive photo


'Harusama Pink'

* photo taken on April 18 2010 @ U.S. National Arboretum, D.C.



'Morasaki-shikibu'



'White Moon'
White flowers, otherwise identical to species.

'Zuiko'
Red flowers, otherwise identical to species.

Azalea linearifolium ( Spider Azalea )
Also called Azalea macrosepalum 'Linearifolium'.
A semi-evergreen to evergreen shrub, reaching a maximum size of 6 x 6 feet.
Some records include: 10 years - 3.3 feet.
The very narrow, linear leaves ( very unusual for an Azalea ) are up to 2 x 0.3 inches in size, and deep green in color.
The unscented flowers are fuschia-pink.
Hardy zones 6 to 8 in partial shade, preferring woodland understory conditions with protection from wind. Requiring moist, light, slightly acidic, well drained soil. Pest and disease resistant.

* photo taken on April 18 2010 @ U.S. National Arboretum, D.C.

* photos taken on Apr 23 2017 @ Brookside Gardens, Wheaton, MD

* photos taken on Aug 5 2017 @ Brookside Gardens, Wheaton, MD


Azalea macrosepalum
A low, spreading, semi-evergreen to evergreen shrub, that is native to pine woods in Japan, where it is rare. Some records include: 4 x 4 feet in 10 years, with an eventual height of 5 feet at most.
The leaves are up to 3 inches in length. The foliage turns attractive orange-red during autumn in cold climates. When temperatures reach the lower teens, it becomes deciduous.
The lavender flowers, up to 2.5 inches across, have very narrow petals. They are borne during mid-spring.
Hardy zones 5 to 9 ( hardy to -15 F, root hardy to -20 F ), requiring moist, light, slightly acidic, well drained soil. Pest and disease resistant. Heat tolerant, thriving in the Deep South.

'Kokomo-shikibu'
More vigorous, reaching up to 6 feet in 8 years.

* photo taken on April 18 2010 @ U.S. National Arboretum





* photos taken on May 7 2014 @ London Town Gardens, Edgewater, MD


'Primitive Beauty'
Similar to species, except more vigorous in habit and bearing pure white flowers.

Rhododendron mucronatum ( Snow Azalea )
A compact, medium size, evergreen shrub, it has been cultuvated for centuries in China and Japan but its origins are unknown as it has not been found in the wild. Some records include: 10 years - feet; largest on record - 10 x 8 feet.
The hairy, oblong leaves, up to 2.5 inches in length, are mid green.
The abundant, fragrant, pure white ( rarely pink ) funnel-shaped flowers, up to 2 inches long, are borne in trusses of 1 to 3 during mid-spring.
Hardy zones 5 to 8, tolerating as low as -25 F. Tolerates and even enjoys full sun.

'Delaware Valley White'
Vigorous growing, dense and rounded; reaching up to 5 x 5 feet in 10 years, eventually to 8 x 7 feet. Growth rates as much as 20 inches have been recorded.
The foliage is glossy, deep green and turns to yellow during autumn.
The lightly fragrant, pure white, double flowers, up to 3 inches across, appear over a period lasting up to 3 weeks during late spring.
Hardy zones 6 to 9 or even 5 if sheltered.

* photo taken on May 6 2011 in Odenton, MD
* photos taken on April 27 2012 in Columbia, MD

* photos taken on May 5 2015 in Columbia, MD

* photos taken on May 9 2015 in Columbia, MD

* photo taken on Aug 11 2015 in Columbia, MD

* photo taken on Nov 17 2015 in Columbia, MD

* photo taken on May 9 2016 in Columbia, MD

* photos taken on Nov 29 2016 in Columbia, MD


Azalea nakahari
A dense, low, prostrate evergreen shrub, native to mountains of Taiwan at elevations of 6500 to 7500 feet. Some records include: 10 years - 1 x 3 feet; largest on record - 2.5 x 4 feet. Excellent for use in rock gardens and borders.
The very small leaves, up to 1 inches in length, are glossy deep green above, light green beneath.
The scarlet-red, funnel-shaped flowers, up to 1.5 inches in width, are borne in trusses of 1 to 3 during early summer.
Hardy zones 6 to 9 ( tolerating -15 ).

'Michael Hill'
Reaches up to 16 inches in 10 years, with frilled, strong light pink ( with purplish-red blotch ) flowers.
Hardy zones 7b to 9

Azalea simsii ( Indian Azalea )
A moderate growing, medium-size evergreen shrub, that is a widespread native from China to Taiwan; south to northern Burma, Laos and Thailand. Some records include: 10 years - 6.5 x 6.5 feet; largest on record - 10 x 10 feet. It can be used in hedging.
The leaves, up to 3 inches in length, are deep green.
The abundant, deep red, broad funnel-shaped flowers, up to 2.5 inches across, are borne in trusses of 2 to 6 during
Hardy zones 7 to 9 ( tolerating as low as 0 F ) requiring good protection from excessive wind. Prefers warm to hot summers.

Azalea taronense
Reaches up to 2 feet in 10 years, eventually 3 feet.
The attractive foliage is glossy deep green.

Azalea tashiroi
A large shrub, reaching a maximum size of 20 feet ( usually under 6 ft. in U.S. ) that is native to woodlands of southern Japan and the Ryukyu Islands. Some records include: 10 years - 3.3 feet.
The leathery, elliptical to oblong leaves, are up to 3 x 1.5 inches in size. The foliage is glossy deep green. The leaves are whorled at the stems.
The pure white flowers, up to 2 inches long, are borne during late spring.
The smooth bark is grayish-brown.
Hardy zones 7 to 9, tolerating as low as 0 F, requiring a warm site. Heat and drought tolerant.

Azalea tschonoskii
A rare, dense, compact, semi-evergreen Azalea, that is native to Kamchatka, Korea and Japan.
The foliage turns to orange and red during autumn.
The small, white flowers appear during early summer.
It is among the most cold hardy Azaleas.

* historic archive photo


Azalea weyrichii
A vigorous evergreen large shrub to small tree, native to southern Korea and southern Japan.
Some records include: 10 years - feet; largest on record - 17 feet with a trunk diameter of 4 inches.
The rounded leaves, up to 4 x 2.5 inches, are reddish-brown hairy at first, turning to green.
The pink, funnel-shaped flowers, up to 2.5 inches across, are borne in trusses of 2 to 4 during spring.
Hardy zones 5 to 9

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