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Rhododendron Ponticum Friend or Foe ?
A nuisance in some woodlands
Notes from a Lancashire Countryman
Rhododendron ponticum is a native species of Asia, Spain, Portugal and Bulgaria. It was introduced to the U.K. as an ornamental shrub originally grown in Kew Gardens. It is a tall gangly shrub, almost tree like in habit, if left to its own devises. It is thought that the majority of these shrubs in the U.K. have their origins in Spain.
As an ornamental plant grown in many large gardens it soon "escaped" over the wall to become established in the wider countryside, particularly in woodlands. However, the habitat varies greatly and they may be encountered on acidic heath land, scrub land, peat land, sand dunes and along roadside verges.
Basic Biology of R.ponticum
It is classed as a shrub or small tree which produces suckers which in aid in its spread. It may attain the height of 5 m rarely specimens of up 8 m tall have been recorded. The foliage is evergreen and between 6-18cm long and up to 5cm wide.
The flowers which are often numerous are of a violet blue colouring trumpet shaped and tubular, they are succeeded by elongated dry capsules which contain a plethora of small seeds.The seeds and suckers allow quick expansion of the species.
The large flowers are impressive
As far as many conservationists are concerned R. ponticum is just another invasive species which is detrimental to native flora and wild life in general.Studies have revealed it reduces biodiversity by forming dense stands which in turn produces dense areas of shade and deep leaf litter. The leaf litter imparts a toxic affect which is thought to last up to 7 years even when the perpetrator has been removed. As a woodland invader the shrub impacts on animals as well as native flora. Many of them rely on the native woodland understory of hazel and hawthorn, both of which are shaded out by this alien shrub. One example is the dormouse, but others include wood mouse, yellow necked mouse and bank voles.
The foliage of R. ponticum is toxic to many herbivores because of a substance they contain called Diterpenes. A less known fact is that honey produced from the flowers of this shrub is known to be toxic to humans. Historical records alledge that Greek soldiers were poisoned after consuming the honey whilst in Asia Minor.
Rhododendron and habitat
Many various ways have been employed in an attempt to eradicate the shrub from habitat where it is thought to be especially detrimental to native species. Digging them out with heavy machinery is not only expensive but in many cases impossible to achieve because of the typeof any habitat they tenant. Likewise cutting them down or trying to grub them out is also impracticable in many cases. Spraying with herbicide is indiscriminate and detrimental to other nearby flora. However, the Forestry Commission faced with these difficulties have come up with a new scheme to eradicate the shrub. They have started injecting herbicide directly into the trunks and stems which results in the demise of the shrub within six months of being applied. This method is precise unlike spraying which as already mentioned is indiscriminate. It also has the advantage that it is not washed away by the rain, which also prevents herbicide from entering the water system. Time will tell if the efforts are a viable and successful.
Rhododendron and the Gardener
Whilst Rhododendron ponticum is not looked upon favourably in the wider countryside cultivated relatives have won the affection in the hearts of many gardeners. To grow them successfully they need to be planted in acidic soil with ample drainage, thus grown in containers these requirements may be fully met.
beautiful Pink flowered variety
Here is a small sample of the rhododendron species that have been cultivated.
RHODODENDRON-"PINK PEARL"--------This species is an open ,upright shrub which may attain the height of 12m or more, it is evergreen and completley frost hardy. They produce bunches of funnel shaped flowers that are of a delightful pink colour providing stunning displays during late summer.
RHODODENDRON "PRESIDENT ROOSEVELT"---This species has a handsome variegatedfoliage and bright red pink flowers.It in named in honor of the 26th president of the United States Theodore Roosevelt.
Other Species Continued
RHODOENDRON "auriculatum" is an evergreen shrub bushy and wide branching up to 20 feet. It is a completley frost hardy shrub that has large onlong leaves with ear like lobes at the base. It produces bunches of 7-15 large, heavily scented flowers, which are funnel shaped. It is another species that flowers in late summer. They grow best in light shade/light woodland.
RHODODENDRON " Queen of hearts" An evergreen, open with a spread of 5-12 feet when mature. it is a frost hardy species. It produces domed branches with a plethora of funnel shaped deep crimson flowers which have black or dark flecks within. This species flowers in mid spring.
RHODODENDRON " Lady Roseberry" Is a stiffly branched, evergreen with a height and spread of up to 5-12 feet when mature. During late spring it produces clusters of drooping,bell-shaped flowers that are waxy in texture, of a deep pink colour which becomes paler towards the petal edges. it is an ideal species for light woodland.
RHODODENDRON " Purple splendour" an bushy evergreen species with a height and spread of around 10 feet when mature. It produces well formed bunches of open funnel shaped flowers, which are of a rich royal purple with dark markings in the throat of the petals. It flowers from late spring and early summer.
RHODODENDRON " Occidentali" also known as the western Azalea a shrub growing up to 5 m tall when mature. The leaves of this species are deciduous they are three to nine cm long and 1-3 cm wide. The flowers are white to pink often accompanied by a yellow blotch.
Pests and Rhododendrons
Rhododenrons may play host to common garden pests such as aphids, leaf hoppers, lace bugs,scale insects and caterpillars. However, all of these may be controlled quite easily and should not deter the gardener from growing these beautiful flowering shrubs.