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Azalea Knaphill Arneson Gem

Rhododendron (Azalea) x knaphill Arneson Gem
Knaphill Azalea, Hybrid Rhododendron

4,2/5
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Dim, 27/06/2023

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A rather compact, yet quite vigorous hybrid azalea that produces large, yellow-orange flowers up to 9 cm (3.5 in) in diameter in May-June. Its bright green, deciduous foliage, takes on beautiful orange autumnal shades. To grow this shrub successfully, give it humus-rich, lime-free, well drained soil that remains slightly moist. It prefers a moderately sunny position. Very hardy.
Flower size
9 cm
Height at maturity
1.50 m
Spread at maturity
1.20 m
Exposure
Sun, Partial shade
Hardiness
Hardy down to -23°C
Soil moisture
Moist soil
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Best planting time March, October
Recommended planting time March to May, September to October
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Flowering time May to June
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Description

Azalea 'Arneson Gem' is a variety of Chinese Azalea with large, bright orange-yellow flowers that are extremely decorative and bloom in clusters towards the end of spring, set off by attractive, soft green foliage. Unlike Japanese Azaleas, this plant is deciduous and very hardy. As well as its vibrant flowers, the shrub also produces beautiful autumn foliage. Too little known and too little used, Chinese Azaleas are very graceful plants with a whole host of qualities, that thrive in lime-free soil. They are a must-have in the garden or in a large pot on the terrace!

 

Azaleas are actually rhododendrons, with flowers having 5 stamens instead of 10. They are plants of the Ericaceous family, just like heathers, preferring lime-free, acidic soils, and humid climates. 'Arneson Gem' is a hybrid cultivar from the Knap Hill series developed in the United States before 2000. This creation received and award in England from the RHS for its ornamental qualities and performance in the garden. It is a fairly vigorous shrub, both graceful and bushy, with an upright habit, reaching about 1.50 m (4 ft 11 in) in height and 1.20 m (3 ft 11 in) in spread by the age of 10. Its flowers abundantly over a long period from late May to June. The star-shaped flowers, 7.5 to 9 cm (3 to 3.5 in) in diameter, funnel-shaped with a ruffled edge, are gathered in terminal clusters of 10 to 15. They are a mix of varying intensities of gold and orange. The deciduous foliage is composed of simple, oval-lanceolate leaves, with smooth edges, arranged alternately on the branches. They vary from 5 to 10 cm (2 to 3.9 inches) in length, and their bright green summer colour turns orange and then red in October before falling. Azaleas and Rhododendrons have a shallow root system that always needs to be kept moist, but they also dislike waterlogged soil which would suffocate the roots.

Chinese Azaleas have fewer requirements than Japanese Azaleas, which are evergreen: they are quite hardy and tolerate sunny positions, and even occasionally dry soil depending on the hybrids. They are at their best, however, in cool climates, with distinct winters, planted in humus-rich, fertile, lime-free soil. They are beautiful shrubs for borders, with a very attractive, natural habit, blooming twice a year. They are a perfect accompaniment to Japanese maples, which also change their appearance with the seasons, as well as Japanese camellias or their graceful, often fragrant, autumn flowering cousins, the C.sasanqua hybrids. The 'Arneson Gem' Azalea will be magnificent when combined with other Chinese Azaleas in shades of yellow, orange, peach, or red. The undeniable beauty of deciduous Azaleas merits the changes needed to create the conditions they love. They can also be grown in a large, carefully chosen pot with suitable compost, and watered with non-alkaline water.

 

Azalea Knaphill Arneson Gem in pictures

Azalea Knaphill Arneson Gem (Flowering) Flowering
Azalea Knaphill Arneson Gem (Foliage) Foliage

Plant habit

Height at maturity 1.50 m
Spread at maturity 1.20 m
Habit Irregular, bushy
Growth rate normal

Flowering

Flower colour orange
Flowering time May to June
Inflorescence Corymb
Flower size 9 cm
Bee-friendly Attracts pollinators

Foliage

Foliage persistence Deciduous
Foliage colour green

Botanical data

Genus

Rhododendron (Azalea)

Species

x knaphill

Cultivar

Arneson Gem

Family

Ericaceae

Other common names

Knaphill Azalea, Hybrid Rhododendron

Origin

Cultivar or hybrid

Product reference1734101

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Planting and care

The Arneson Gem Chinese Azalea thrives a sunny location, unlike the Japanese Azalea,but its favourite position is in partial shade or east-facing for the morning sun, especially in very hot or sunny regions. Plant it in ericaceous or humus-rich soil, moist but well-drained, and above all, lime-free. Make sure not to plant the root ball too deep, it should be level with the ground. Water copiously during dry periods, at least once a week during the first year. In spring, apply fertilizer for ericaceous plants. Pruning is not essential but it is a good idea to prune lightly after flowering to keep the plant looking neat. Remove spent flowers to encourage new growth. The Azalea suffers from very few diseases when well-established outdoors. It can be attacked by weevils that eat the edges of the leaves and rootlets, and by the famous "Rhododendron lace bug", though not often causing significant damage. If the soil is chalky or poorly drained, or if the rootball is too deep, the leaves may turn yellow and eventually die.

Some cultivars are quite susceptible to powdery mildew.

Planting period

Best planting time March, October
Recommended planting time March to May, September to October

Intended location

Suitable for Meadow, Woodland edge
Type of use Border, Free-standing, Container
Hardiness Hardy down to -23°C (USDA zone 6a) Show map
Ease of cultivation Amateur
Planting density 3 per m2
Exposure Sun, Partial shade
Soil pH Acidic, Neutral
Soil type Silty-loamy (rich and light)
Soil moisture Moist soil, rich and very well-drained

Care

Pruning instructions Simply remove the faded flowers, by pinching them out , to protect the forming buds. This Azalea does not require pruning.
Pruning Pruning recommended once a year
Pruning time June
Soil moisture Moist soil
Disease resistance Good
Overwinter Can be left in the ground
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