Rhododendron

Important introduction

The rhododendron, together with the azalea, embodies the representative par excellence of the plants belonging to the Rhododendron genus: we are talking about small shrubs of the Ericaceae family, typical of America and Europe. Often, rhododendrons are confused by azaleas: it is necessary to clarify this. Both plants are members of the same family and of the same genus, but the rhododendrons have more impressive dimensions, more important masses and persistent leaves (the leaves of the azaleas are deciduous).

In general, all plants belonging to the Rhododendron genus are grown mostly for ornamental purposes; however, in the extensive varietal landscape - including over 500 rhododendron trees or shrubs - some species are used in both herbal medicine and homeopathy, given the many medicinal virtues.

Toxic plant?

It should be remembered, however, that the excessive intake of rhododendron extracts can cause serious side effects in the body: not surprisingly, in toxicology, the rhododendron is one of the incriminating plants to trigger toxic effects, therefore labeled as potentially dangerous. In any case, the use of rhododendron for therapeutic purposes is supported by rather satisfactory pharmacological validations; therefore, its use is not banned.

Botanical varieties and properties

As we have seen, there are many species of rhododendrons: in order not to generalize, the most important ones are listed below, all differentiated by peculiar and distinguishable characters.

1. Rhododendron ferrugineum : it represents the most common species of rhododendrons, also better known as rose of the Alps. We are talking about a small evergreen tree (shrub), which generally does not exceed 50 cm, but sometimes can reach one meter thanks to the particularly tortuous branching . These species are recognized, in particular, by large and developed flowers, with a characteristic bell-shaped shape; the color of the flowers varies from pink-fuchsia to ruby ​​red, an element that distinguishes this species from all others. The rhododendron sp. ferrugineum sports leathery leaves, painted red on the underside. The plant contains tannins and arbutin; in herbal medicine, the decoction of leaves and dry branches of rhododendron sp. ferrugineum has diuretic, sudorific, antirheumatic and calming properties. [taken from Dizionario ragionato of herbal medicine and phytotherapy, by A. Bruni, M. Nicoletti]

2. Rhododendron hirsutum : among the dense foliage of the forests of the central-eastern Alps and the Asian mountains, this variety of rhododendrons cannot go unnoticed. The stem, which does not exceed 50-80 cm in height, has ramifications developed above all in the apical part, from which numerous leathery leaves with a mostly elliptical shape, persistent and tormenting at the margins branch out. The beautiful flowers are pink, generally grouped in racemose inflorescences called corymbs. The leaves contain important active ingredients, including ercolina and arbutin (bitter glycosides); because of the presence of these active ingredients, the rhododendron has diuretic and diaphoretic properties, that is to say able to increase body sweating.

3. Rhododendron chrysanthum : typical of the Asian regions, this rhododendron is used in particular in the phytotherapeutic field for its hypotensive, antirheumatic, antitussive and expectorant properties. This variety is also used in homeopathy: the mother tincture obtained from leaves and branches is useful in case of neuralgia and rheumatic pains. These properties are attributed to the rhododendron due to the presence of some chemical constituents, such as: andromedotoxin (tetracyclic diterpene), canferolo, quercetin, hyperoside (flavonoids), arbutin, essential oil and citric acid.

Other species of rhododendron are used as antivirals (eg Rhododendron aureum ) and antirheumatic (eg Rhododendron maximum ).

Those just described are just some of the many varieties of rhododendrons currently identified in botany; however, the various species are all joined by magnificent and showy blooms, which exhibit themselves maliciously preening among the green spaces of nature.

Rhododendron and toxicology

Already in the times of Pliny the toxicity of rhododendrons was known, eclipsed by the elegance and charm of their colorful flowers. Even the bees, fond of nectar, have always been attracted by the flowers of the rhododendron, and together they cooperate to produce honey: at the time of the ancient Roman army - precisely during the Asian campaign - there was an intoxication of the soldiers following the assumption of excessive doses of rhododendron honey.

However, the probability of taking "toxic" honey obtained from rhododendron flowers is very low because the nectar of this plant is mixed with countless varieties of other flowers; consequently, the danger of toxicity is almost averted.

In general, among the symptoms of acute or chronic toxicity generated by the immoderate intake of rhododendron extracts, we recall: nausea, vomiting, diarrhea, abdominal pain, neurological disorders and, in case of severity, cardiovascular collapse.

To give an example, the rhododendron sp. hirsutum may contain toxic diterpene molecules (having an andromedan nucleus), which are responsible for possible states of hypotension, spasms, bradycardia, heart failure.

All parts of the rhododendron plant contain andromedotoxin, due to hypotension and long-term damage to heart function. Clearly, the aphorism "is the dose that makes the poison" once again valid: which means that the subject can report damage only after taking excessive amounts of rhododendron extract.

"The lack of evidence of toxicity does not equate to evidence of lack of toxicity"

Rhododendron in a nutshell »