Rhododendron ponticum

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schedule 9

Rhododendron (Rhododendron ponticum) is an established non-native invasive species within the UK, threatening a variety of habitats and the associated flora and fauna.

It was first introduced to the UK via Gibraltar in 1763 and by 1893 it was sold in London markets as a flowering pot plant. R. ponticum was first recorded in the wild in 1894, as it had escaped from horticulture and been planted in woods for game cover.


Rhododendron ponticum and the hybrid Rhododendron ponticum x Rhododendron maximum are listed under Schedule 9 to the Wildlife and Countryside Act 1981 with respect to England and Wales. As such, it is an offence to plant or otherwise allow this species to grow in the wild


Potentially toxic chemicals, particularly 'free' phenols, and diterpenes, occur in significant quantities in the tissues of Rhododendron ponticum. Diterpenes, known as grayanotoxins, occur in the leaves, flowers and nectar.

It is recommended that this plant is controlled or eradicated, and you have a duty of care to prevent its spread from your property. You must handle and dispose of the plant in accordance with strict guidelines and legislation.

Rhododendron Control, Survey & Treatment Specialist

Japanese Knotweed Ltd are experienced contractors in the surveying and remediation of invasive non-native plant species. We will survey a site and establish the best method and price for control or eradication in accordance with the client’s requirements and any change of site use plans. Works are expertly undertaken by trained and certified operational staff, with all works fully recorded. By contacting us you benefit from:

If you suspect you have an invasive non-native species but are unsure, please send photos of the plant to ident@knotweed.co.uk for free identification.

Rhododendron Identification

Rhododendron in the wild
Rhododendron in the wild
Rhododendron flowers
Rhododendron Flowers
Herbicide treatment of Rhododendron
Rhododendron Bush

About - Rhododendron

R. ponticum is native to countries in the western and eastern Mediterranean such as Spain, Portugal and Turkey and occurs eastwards through Asia into China. It is not native to Britain but was first introduced in the late 18th century. It became especially popular on country estates in Victorian times, providing ornamental value, as well as cover for game birds.
R. ponticum is an evergreen shrub often reaching 4-5m in height at maturity (even up to 8m in the correct environment). These shrubs have light brown, woody stems (which develop into trunks over time) and elliptical, glossy, dark green leaves. Key features include:

Dangers - Rhododendron

Rhododendron can have damaging effects on the local environment. By growing rapidly this plant outcompetes native flora, decreases biodiversity and is a sporulating host to Phytophthora ramorum and Phytophthora kernoviae.

Phytophthora caused the Irish potato famine and more recently, is responsible for Sudden Oak Death. Since its initial identification in the UK, Phytophthora has been detected in the south-west of England, Wales and Northern Ireland.

As previously stated, Rhododendron produces toxic chemicals making the whole plant toxic to humans and animals, including livestock. There is also evidence of allelopathy, which may include the inhibition of germination or of the establishment of the seedlings of competing species.

Rhododendron UK

The active growth of Rhododendron is from early March to October, with a flowering of lilac or pink flowers taking place between May and June. Seed dispersal takes place generally between February and March (8-9 Months after flowering). The plant spreads by seeds and regeneration from rhizome segments and stem layering. It’s estimated that each inflorescence can be responsible for up to 7000 seeds, which can give rise to an enormous seed bank in the soil.

Physical clearance and removal of shrubby material are insufficient if subsequent basal regrowths and generation of seedlings from seed in the ground are not also treated with appropriate herbicides. Rhododendron prefers moorland, woodland, rocky outcrops and acidic soils.

Rhododendron Diseases

Rhododendron can become infected with several fungal diseases, causing unattractive foliage or a lack of flowers. The most substantial diseases are powdery mildew (Erysiphe spp.), bud blast (Seifertia azalea) and petal blight (Ovulinia azalea). When Rhododendrons are affected by the powdery mildew disease, the actual growth of the fungus can be hard to detect. However, infection tends to cause reddish-purple, yellowish or pale green patches on the upper surface.

The symptoms of bud blast include the flower buds going brown and dying but remaining attached to the plant. As the disease develops, the buds may turn silvery grey before coming covered in black bristles. Petal blight causes infected flowers to spawn leaf spots on the petals under wet conditions, which spread quickly and causes the petals to collapse in a wet, oily mess.


NB: If no target invasive weed is found on the property a charge of £165 plus VAT will apply.
*If the area to be surveyed is greater than 1 acre we reserve the right to apply a charge to carry out the survey. For the Isle of Man or Isle of Wight charges may apply. Price on request.

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