Genus Rhododendron (Rhododendron)
The largest genus in the family, includes over 1000 species. These are shrubs, less often small trees. The leaves are arranged alternately. Flowers in umbellate or corymbose inflorescences, rarely single or two, large in most species. The calyx is small, 5-split or 5-notched. Corolla somewhat zygomorphic (bilaterally symmetric) or almost regular, wheel-shaped, funnel-shaped, bell-shaped or almost tubular, 5-lobed (rarely 6-10-lobed). The color is very varied. The fruit is a capsule, the seeds are small, numerous. One of the most decorative and popular plant groups.
Group Scaled rhododendrons
The leaves are covered with scales, especially on the underside of the leaves (it seems that the underside of the leaf is covered with small dots). The leaves are evergreen, in some species they are semi-evergreen. In rhododendrons of this group, the leaves at the base and at the end are more pointed, smaller and at the ends of the shoots are located less frequently than in other groups.
Rhododendron dense (Rhododendron impeditum)
Homeland - the mountains of China. Evergreen shrub 0.3–0.6 m high (we have 0.4 m). Shoots are short, covered with scales. Leaves are broadly elliptical, 1.5–2 cm long and 1 cm wide, strongly scaly. Flowers 1-2. Corolla broadly funnel-shaped, violet-blue, 2–2.5 cm in diameter. 10 stamens, hairy pubescent at the base. The column is crimson. Blooms in May – June.
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The seeds ripen. Winter-hardy. Tested 4 samples, now in collection 1, received in 2000 from Moscow. One of the most common and resistant small-leaved and small-flowered dwarf evergreen rhododendrons in culture.
The form: ‘Luisella’
Our height is 0.5 m, the crown is compact. In the inflorescence 5-6 (8) flowers up to 3 cm in diameter (larger than the original species), purple-violet, pale pink column. Blooms in May – June. Winter-hardy. The collection contains 1 sample, obtained in 2001 from Moscow.
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Sikhotin rhododendron (Rhododendronsichotense)
Homeland - the Far East (Sikhote-Alin). Semi-evergreen shrub up to 0.5–1.5 m high (we have 1 m). Leaves are elliptical-ovate, 1.7–3.5 cm long, on sterile shoots up to 4.5 cm, with a blunt, sometimes notched tip and a wide base, olive green, covered with scaly glands, shiny and aromatic. In autumn, most of the leaves roll into a tube and hibernate, a small part falls off. Flower buds are 1-4, 1-2-flowered. Flowers appear before new leaves bloom. Corolla pink-violet, 2.1-2.7 cm long and 3-4.5 cm in diameter, with overlapping wide lobes that are 1/2 of the corolla length. Blooms in April – May.
The seeds ripen. Relatively winter-hardy, sometimes the ends of annual shoots freeze slightly, flower buds are damaged in severe winters, but it suffers more from winter thaws and spring frosts. 5 samples have been tested, now in collection 1, a reproduction of the sample obtained in 1992 from a sample from nature (Khabarovsk Territory).
Group Scalloped Rhododendrons
Leaves are evergreen, leathery, 4–30 (!) Cm long, less often shorter, from above in most cases glabrous, often smooth and shiny, from tomentose to glabrous below, leaf edges are often curled. Along with clumpy hairs, glandular hairs are also found.
Short-fruited rhododendron (Rhododendron brachycarpum)
Homeland - Korea, Japan.
Evergreen upright shrub, at home 2–4 m tall (we have 1.8 m, spreading crown, with raised branches). Young shoots and leaves are finely gray-pubescent, but the pubescence quickly disappears. Leaves are oblong-lanceolate, 8–20 cm long and 3–5 cm wide, obtuse, with a curled edge, with a grayish or brownish felt underside and a yellowish-green central vein. Flowers 10–20 in rounded inflorescences. Corolla 4–5 cm in diameter, white, cream or slightly pinkish, with greenish or brown dots. Blooms in June – July.
The seeds ripen. Winter-hardy, flower buds are damaged in severe winters. Tested 5 samples, now in collection 4, received in 1981, 1982. from Tokyo (Japan), Arboretum Novy Dvor (Opava, Czech Republic) and Essen (Germany).
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Short-fruited rhododendron Fori (Rhododendron brachycarpum ssp. fauriei)
Homeland - the Far East, South Korea, Japan.Evergreen shrub, in culture 1-3 m tall (we still have 1.5 m), at home a tree up to 3-5 m or elite up to 3 m. Young shoots with soft brownish pubescence. Leaves are leathery, 6–15 (20) cm long and 2–5 cm wide, longitudinal-lanceolate, obtuse or pointed, dark green above, shiny, lighter below. Flowers 5-15 (20). Corolla 2–2.5 cm long, 2–4 cm in diameter, white with a pinkish tinge, with greenish or brown specks. Blooms in June – July.
The seeds ripen. Winter-hardy, in severe winters the ends of annual shoots freeze slightly. There are 2 samples in the collection, obtained in 1983 and 1989. from Kiev and Moscow.
Large-leaved rhododendron (Rhododendronmacrophyllum)
Homeland - North America. Evergreen erect shrub up to 3 (6) m in height (we have 1 m). Leaves are elliptical to oblong, with a pointed apex and wedge-shaped base, glabrous, 7–20 cm long and 3–5 cm wide, the greatest width is below the middle of the leaf. Flowers of 20 or more in dense inflorescences up to 15–20 cm in diameter. Peduncles up to 5 cm long, glabrous, white-pubescent calyx. Corolla about 4-6 cm in diameter, broadly campanulate, with wavy lobes along the edges, from pale pink to pink-purple, with reddish-brown specks, occasionally white. The ovary is silky white. It is close to the Katevba rhododendron, sometimes considered as its western form, characterized by more upright growth, color of flowers, pubescence of the ovary, bare pedicels and leaf shape. Blooms in May – June.
The seeds ripen. Relatively winter-hardy, sometimes the ends of the shoots freeze slightly, perennial wood is damaged in severe winters. Tested 7 samples, now in collection 2, reproduction 1993 and 1995. samples obtained from Salaspils (Latvia) and St. Petersburg.
Katevbinsky rhododendron (Rhododendron catawbiense)
Homeland - North America. Evergreen shrub 2-4 m tall (we still have 1 m), the diameter of the bush usually exceeds the height. (Photo 176.) Young shoots are usually pubescent, later glabrous. Leaves are elliptical to oblong, 6–15 cm long and 3–5 cm wide, widest in the middle of the leaf, obtuse at the apex, with a rounded base, dark green, shiny. Flowers 15–20 in inflorescences up to 15 cm in diameter. Corolla about 6 cm in diameter, funnel-bell-shaped, with wide rounded lobes, pink or lilac-lilac with greenish specks. Ovary with rusty tomentose pubescence. Blooms in May – June.
The seeds ripen. Stable in culture, widely used in breeding and as a stock for varietal rhododendrons. Winter-hardy, in severe winters the ends of annual shoots freeze slightly. Tested 9 samples, now in collection 4, received in 1981-1990. from Tallinn (Estonia), Kiev (Ukraine), Kalsnava and Salaspils (Latvia).
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Pontic rhododendron (Rhododendron ponticum)
Homeland - Balkans, Caucasus, Syria, Lebanon. Evergreen shrub or tree 2–6 (rarely 8) m high (at home, we have 0.6 m), crown diameter up to 5 m. Young shoots are pubescent, later glabrous. Leaves 9–28 cm long, longitudinally lanceolate, shiny, glabrous. The flowers are funnel-shaped bell-shaped, lilac with yellow dots, up to 6 cm in diameter, in the inflorescence of 10-15 flowers. Blooms in May – June.
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Heat-loving. Tested 12 samples, now there are 2 samples in the collection. Obtained in 1996 from nature does not bloom, perennial shoots freeze every year. A reproduction of a sample obtained in 1997 from Kiev has formed a creeping form, usually hibernates successfully, blooms and bears fruit, perennial wood suffers in severe winters.
Rhododendron Smirnov (Rhododendron smirnowii)
Homeland - Georgia (Adjara), Turkey. Evergreen shrub 1–1.5 m tall (we have 0.9 m). Young shoots are densely white-tomentose. Leaves are longitudinal-elliptical, 8–15 cm long and 2.5–3 cm wide, obtuse at the apex, narrowed towards the base, with a slightly curled edge, glabrous above, clumpy white-tomentose below, petioles 1–2.5 cm long. Pedicels up to 4–5 cm long, tomentose pubescent. Corolla purple-pink, 4–6 (7) cm in diameter, broadly funnel-shaped with a wavy edge, dense white tomentose ovary. It blooms with us in June.
The seeds ripen. Winter-hardy, in severe winters the ends of shoots and flower buds freeze slightly. Tested 12 samples, now in collection 2, received in 1993 and 1998. from Leipzig (Germany) and Tartu (Estonia).
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Read also:
- Deciduous rhododendrons
- Rare rhododendrons
- Hybrid rhododendrons
Photo by the author
