Azalea - Rhododendron

Azalea - Rhododendron

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Azaleas and Rhododendrons

Azaleas and rhododendrons belong to the same botanical genus, the rhododendron genus, which brings together about five hundred species of shrubs of various sizes, originating in Asia, Europe and nor America, belonging to the Ericaceae family. In the gardens we can admire the various hybrids, born from the cross between the most decorative species, or with the most showy flowering.
The rhododendron are shrubs, ranging from a size of about 25-30 cm, up to the real trees, up to 3-4 meters high. They have deciduous or evergreen foliage, with an oval shape and a dark green color. The flowering occurs, for the species cultivated in the garden, in April-May, however in the beginning of spring; there are also species with summer flowering and others with late winter flowering. Azaleas grown in apartments are generally forced to bloom at any time of the year, so that they can be sold.

Rhododendron cultivation from outside

Although the species are innumerable, in general the rhododendrons that are cultivated in the garden have similar needs. These are evergreen or semi-evergreen shrubs, which prefer sunny positions; they do not fear the cold and can withstand even intense and prolonged frosts. To develop they need a specific soil for acidophilic plants, an excess of limestone in the soil or the lack of iron available for the plants causes the rapid development of chlorosis, or the yellowing of the foliage, with consequent poor flowering and general decay of the plant.
If the spring is sparsely rainy it is advisable to water our rhododendrons, repeating the operation from time to time, but insisting during the hottest periods of the year: we avoid leaving the soil completely dry for long periods of time, especially as regards the rhododendrons of mountain origin.

Rhododendron from inside

The less rustic species are grown in the apartment; they prefer bright locations, but not directly exposed to sunlight, and need regular watering, in order to keep the soil perpetually moist. During the hottest days of the year or when the heating is active we vaporize the leaves with demineralized water, avoiding this operation during flowering, since the corollas are very delicate and easily stained. In summer they can be placed outdoors, in a place sheltered from the wind and slightly shaded.
Also indoor specimens need specific soil for acidophilic plants.

Azalea - Rhododendron: The species of rhododendron

If we go to a nursery to buy an outdoor specimen it is very likely that we will find only two "types" of rhododendron, called: rhododendron one, azalea, the other.
In reality they are hybrids, the so-called rhododendrons, with spherical bunches, large dark green leaves, completely evergreen, they are actually species derived from the hybridization of some botanical species; in general they are species derived from R. maximum, R. arboreum, R. argenteum, R. campanulatum, or from other evergreen species, often native to north america and Asia.
Sometimes it is also possible to find specimens of rhododendrons of European origin, such as R. ferrugineum: a small rhododendron, with small persistent leaves of light green color, with deep pink flowers, present on the Alps and the pre-alps.
The so-called azaleas instead belong to a rhododendron subgenus, called azaleastrum; the azaleas that we can find in the nursery are generally hybrids obtained from the Japanese species, they are in fact often gathered under the name of azalea japonica; in reality they are hybrids of R. obtusum, or other similar species. They are semi-evergreen rhododendrons, with small flowers that bloom at the beginning of spring completely covering the shrub; azaleas are smaller than other outdoor rhododendrons, they have more minute and less coriaceous foliage.
Among the outdoor azaleas we also remember the azaleas mollis, these are hybrids of rhododendron japonicum and rhododendron nudiflorum; these are very particular azaleas, first of all in the color, which goes from yellow, to orange, to red; moreover they are completely deciduous and often the flowers bloom before the foliage, with a cascade of color among the branches still dry from the winter; the flowers of these azaleas are also slightly larger in size and often bloom in bunches.
Indoor azaleas, called azalea indica, are hybrids of more delicate species, originating in China, such as R. indicum, R. mucronatum, R. simsii. They are species that fear the cold, evergreens, quite delicate; they should therefore be grown in the apartment.