Types And Varieties Of Rhododendrons

2024 Author: Sebastian Paterson | [email protected]. Last modified: 2023-12-16 13:47

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Rhododendron Finnish grade "Tigerstedt"

Rhododendrons are amazingly beautiful shrubs that are still not widespread in our gardens. Many gardeners are sure that these are very whimsical and difficult plants to grow.

However, our close neighbors in Finland and the Baltic States have a lot of rhododendrons, not only in gardens, but also on city streets, in parks and squares.

This means that rhododendrons can grow successfully in our country. You just need to figure out which species and varieties are suitable for our climate, and learn how to properly care for them.

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In my garden in the northern suburb of St. Petersburg, rhododendrons have been growing for many years, they winter successfully and bloom profusely every year. In this article, I want to share my experience of growing these wonderful plants.

Rhododendrons (lat. Rhododéndron) are a genus of plants in the Heather family, uniting about eight hundred species of evergreen, semi-deciduous and deciduous shrubs and trees. In evergreen species, leaves can remain on the plant for 3-6 years, in semi-deciduous species - one year, and in deciduous species, as usual, from spring to autumn.

The shape of the leaves of rhododendrons is varied - ellipsoid, spear-shaped, round, and the flowers, collected in corymbose inflorescences, also differ in a variety of shapes, sizes and colors. In nature, rhododendrons are found in the Far East, in the mountain forests of Japan, China and other places. On the basis of wild-growing species, numerous varieties have been obtained that are used as garden, greenhouse or indoor plants. In our climate, only a small part of a huge number of different species and varieties can grow successfully, but there are enough of them to make our gardens colorful and unique.

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Rhododendron yellow

Before considering the types and varieties of rhododendrons, I want to understand the name "azalea", which is often used as a synonym for the word rhododendron or to refer to certain groups of rhododendrons. Deciduous rhododendrons are often called azaleas, leaving the name "rhododendrons" for evergreens, which only confuses gardeners.

It is generally accepted to call indoor rhododendrons azaleas, and the hybrids of the Indian or Sims rhododendron are called "Indian azaleas", and the Japanese varieties of the blunt rhododendron "Japanese azaleas". As greenhouse or indoor varieties, hybrid varieties of Indian and Japanese azaleas are usually grown. Recently, semi-deciduous varieties of Japanese azaleas for open ground have appeared, however, it is not yet clear whether they can grow in open ground in our country.

It should be borne in mind that ground "Japanese azaleas" do not belong to the "Japanese rhododendron" species, which is widespread in our gardens. So, the botanical name "rhododendrons" can be applied to any species and varieties of this plant, and the more commercial - "azalea" - only to certain varieties, mostly indoor.

In this article, I only consider cold-hardy species and varieties of rhododendrons that grow and bloom well in our climate, do not require too much maintenance and can be recommended for growing in our gardens. Most of the species and varieties in question grow in my garden.

Classification of rhododendrons

Deciduous rhododendrons

Rhododendrons Daurian (Rhododendron dahuricum) and Ledebura (Rhododendron ledebourii) are close to each other, although Ledeboura is considered semi-leafy, since its old leaves remain until spring. Both plants bloom in early spring before new leaves grow, usually in late April - mid-May. The color of flowers is most often lilac, flowering is very abundant. Now, in addition to species plants, varieties are also appearing.

Plants can grow to a height of 2 meters or more. Daurian rhododendron is spreading, takes up a lot of space, and Ledebour's rhododendron is more erect, compact. These rhododendrons are unpretentious - they can grow in the sun and in partial shade, on acidic soils common to all rhododendrons, and on ordinary garden soils. They are quite cold-resistant, but they do not tolerate long winter thaws. Flower buds swell when the temperature rises and can freeze when the temperature drops, after which the spring bloom disappears.

Rhododendron canadian

Rhododendron canadense (Rhododendron canadense) is a very interesting, but not common enough species. It is compact, up to 1 meter tall, blooms very profusely in the early stages, usually in early May. Lilac flowers of an unusual shape. Small, elongated, slightly bluish leaves grow back during flowering. The bush is decorative after flowering. Rhododendron canadian is very unpretentious to soil and lighting, it blooms almost every year.

Japanese rhododendron (Rhododendron japonicum) is a deciduous, highly branched shrub, usually up to 1 m high. Leaves up to 10 cm long, 2-3 cm wide. Flowers 6-8 cm in diameter are collected in inflorescences of 6-12 pieces. They are usually salmon red with a large yellowish-orange spot, and there are varieties with pink and creamy yellow flowers. Japanese rhododendrons bloom in late May - early June, simultaneously with the blooming of the leaves. Duration of flowering is about three weeks, the annual growth is 20-25 cm. In autumn, the leaves are painted in yellow and purple tones. It is one of the most common rhododendrons in the culture. Fully winter-hardy. On its basis, a large number of winter-hardy deciduous rhododendrons with various flower colors were obtained.

Rhododendron yellow (Rhododendron luteum) is a deciduous branched shrub up to 1-1.5 m high, growing strongly in width (up to 2 m). Flowers - 7-12 pieces per inflorescence - very fragrant golden yellow. Rhododendron yellow blooms in early June, before the leaves open, flowering lasts about 2-3 weeks. This rhododendron grows quite quickly, up to 25 cm per year. It is not very picky about the composition of the soil (it grows even on neutral loam). Completely winter-hardy species, winter-hardy varieties are also based on yellow rhododendron.

Rhododendron Schlippenbach

Rhododendron Schlippenbach(Rhododendron schlippenbachii) is a flowering, rather large, spreading deciduous shrub. It often grows in the form of a tree, reaching a height of 1-1.5 m. The leaves are soft, falling, collected in five at the ends of the shoots, broadly obovate. Above, the leaves are dark green, almost glabrous, below - with rare pubescence along the veins. The flowers are large (7-10 cm in diameter) with a wide bell-shaped pale pink corolla, with specks inside, collected in 3-6 umbellate inflorescences. They have a delicate scent. The Schlippenbach rhododendron blooms simultaneously with the blooming of leaves in May, before the yellow and Japanese rhododendrons. It is frost-hardy, but winters better under snow, especially flower buds. I, if possible, bend it to the ground for the winter. It is one of the most beautiful deciduous species, but is still not very common in our gardens. It is very good in single landings and in small groups.

Among deciduous rhododendrons, varieties from the Lights series - Northern hi-lights, Rosy lights, Mandarin lights, Lemon lights, Orchid lights and others, having a variety of flower colors - are especially winter-hardy and resistant in our climate.

Evergreen large-leaved rhododendrons

Short-fruited rhododendron (Rhododendron brachycarpum) is a large evergreen erect shrub 1.5-2.5 m high. The leaves are large, oval, up to 10-18 cm long and up to 6 cm wide, dark green, glabrous above, shortly pubescent below. They look like the leaves of the large-flowered magnolia. Flowers (about 4 cm in diameter) are collected in large inflorescences, 5-10 (15) flowers each. It is widely used to create varieties of winter-hardy evergreen rhododendrons.

Ketevbin rhododendron

Rhododendron catawbiense (Rhododendron catawbiense) is an evergreen shrub 2 m high with oval, oblong, leathery leaves up to 15 cm long, dark green above and bluish below. The flowers are large, lilac-purple with a wide bell-shaped corolla, very colorful at the time of flowering.

One of the most hardy evergreen rhododendrons. In addition to species plants, the garden form (variety) of Grandiflora with larger lilac flowers is often found in gardens. Katevbinsky rhododendron is often used to create new varieties.

Smirnov's rhododendron (Rhododendron smirnovii) is an evergreen shrub or a small tree up to 2 m tall with white-pubescent young shoots. It has short petiolate, oblong-elliptical leaves, up to 15 cm long, glabrous, green above, whitish-tomentose below; old leaves underneath are light brown, felt. Pink bell-funnel-shaped flowers up to 6 cm in diameter are collected in compact, multi-flowered heads at the ends of the shoots. Frost-hardy, like other species, needs a well-drained nutritious humus soil and a semi-shady location. On its basis, many winter-hardy varieties have been obtained.

Finnish rhododendron variety "Mikeli"

Tall evergreen rhododendrons of Finnish selection based on short-fruited rhododendron grow very well here and bloom every year: varieties Peter Tigerstedt, Helsinki University, Haaga and Mikkeli, as well as low-growing varieties up to one meter high: Hellikki, Elviira, Pohjolan Tytar.

Often in the literature, a group of small-leaved evergreen rhododendrons is also considered, which can grow in our conditions in the open field. But I do not have my own experience of growing such rhododendrons, and there is no reliable literary information about the features of their cultivation.

In my garden in the northern suburbs of St. Petersburg, both deciduous and evergreen rhododendrons - species and Finnish varieties - grow well. But, of course, deciduous rhododendrons are much less whimsical and require minimal maintenance.

Thus, beginner growers, as well as those whose plots are not very suitable for growing rhododendrons, can be recommended to grow deciduous species: Canadian, yellow and Japanese and varieties close to them, especially Finnish selection. If there is a desire to grow more capricious species and varieties, you need to prepare a place that meets all the needs of these plants, and be ready for careful and proper care of them. We will talk about this in the next part.

Read the next part. Choosing a place and planting rhododendrons, growing conditions →

Tatyana Popova, gardener

Photo by Vladimir Popov

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