JARS v54n2 - Rhododendrons in the Former Soviet Union: Eastern Carpathian Species, Rhododendron myrtifolium

Rhododendrons in the Former Soviet Union: Eastern Carpathian Species, Rhododendron myrtifolium
Mieczyslaw Czekalski, August Cieszkowski
Department of Ornamental Plants
Agricultural University
Poznan, Poland

Malgorzata A. Florkowska, Orville M. Lindstrom
Department of Horticulture
University of Georgia Experiment Station
Griffin, Georgia USA

Five Caucasian species of rhododendrons of the former Soviet Union were described in the spring 1998 issue of the Journal (13). The description included Rhododendron caucasicum Pall, R. ponticum L., R. smirnowii Trautv., R. ungernii Trautv., and R. luteum Sweet. To continue this series, we will provide a description of R. myrtifolium based on the Russian literature and our personal observations. The first, third and fourth authors of this article are the chairman and members of the Polish Erica Polonica Group, respectively. In the spring of 1997, they were part of the plant exploration group that traveled to Ukraine and visited the Carpathian Mountains to observe natural stands of R. myrtifolium .

The part of Ukraine that we traveled through, especially the Carpathian Mountain region, was isolated from the world during the cold war era. The area was completely cut off from foreign visitors because of the Soviet military base that existed there. Even people that lived there could not freely travel, not only abroad, but also within the former Soviet Union. They needed travel permits. Our plant expedition in the area was one of the first international expeditions since 1939. We all felt very special to be able to walk and explore an area that was inaccessible for almost half a century.

In 1851, two Austrians, Schott and Kotschy, described Rhododendron myrtifolium for the first time. Thirty-five years later Simonkai described R. myrtifolium under the name R. kotschyi Simonk. Today, the species is widely known as R. kotschyi Simonk. (26). Davidian also used the R. kotschyi name in his work (14). In the older botanical literature, the names R. alpinum Lerchenfeld, R. ferrugineum L. var. myrtifolium Schroet, R. hirsutum Baumg. non L. and R. ferrugineum var. kotschyi can be found (18). We will use the R. myrtifolium name following Cullen (11) and Encke et al. (16), which is also in compliance with the International Code of Botanical Nomenclature (17) and the International Code of Nomenclature for Cultivated Plants (27).

Rhododendron myrtifolium , a tertiary relic of the mountains, is the sole representative of the genus Rhododendron in the Carpathian Mountains region. It belongs to the Holarctic realm, mid-European element, high mountain region, and Carpathian-Baltic range type (23). According to Popov (24), this species is a Pleistocene immigrant from the Arctic, of late tertiary origin.

Rhododendron myrtifolium is a member of subgenus Rhododendron , lepidote group, Ferrugineum series (11). ¹ It is an evergreen, dense shrub, with lower branches often spreading to the ground, growing from 30-50 cm tall. Leaves are elongated, obovate, from 1.5-2.3 cm long and from 0.5-0.8 cm wide, with acute or obtuse apices, lightly crenate at margins, dark green above and ferrugineous scaly beneath. Flowers, with three to seven petals covered with fine hair, are pink, rarely light pink or white ( R. myrtifolium form album [Millais] Rehd.), with funnel-form corollas. Corollas are 1 -1.7 cm wide with their tubes from 0.9-1 cm long. The flowers contain ten anthers that are shorter than the corollas. The stigmata are of the same length or shorter than the hairy ovaries (Figure 1). In Polonina Pozyzevska (Carpathian Mountains) one shrub of R. myrtifolium was found having flowers with increased number of petals. According to Lazarenko (20), the transformation of stamens may explain the development of additional petals in that particular plant. A more complete description of the morphological characteristics of this species is provided by Davidian (14). Our description of R. myrtifolium was based, in part, on personal observation of plants that came from the Southern Carpathian Mountains in Romania. The first author received the plants from Hanna Straus, an employee of the Dendrological Institute of the Polish Academy of Sciences in Kornik, Poland. Rhododendron myrtifolium share some similar characteristics with R. ferrugineum L. Both have dark, shiny green upper leaf surface, scales on the lower leaf surface, and tubular corollas with spreading lobes. However, R. myrtifolium is smaller in stature, has smaller leaves, narrower corolla tubes, and shorter styles than R. ferrugineum (10). The flowers of R. myrtifolium may bloom anytime from mid-May to mid-June depending on the weather and elevation. For example, in 1997 spring arrived late into the Carpathian Mountains, and the rhododendrons first bloomed about the 10th of June (Figure 2).

The present natural growing range of Rhododendron myrtifolium is very limited. It grows in the Eastern Carpathian Mountains region (Ukraine), in the Southern Carpathian Mountains (Romania), and in the Rhodope Mountains (Bulgaria and Greece). It is generally found at subalpine levels at heights from 1500-2500 m above sea level; however, in the Eastern Carpathian Mountains it also grows in the alpine zone (Figure 3). In Ukraine, R. myrtifolium can be found growing in compact groups on the northern and southern slopes (1500-1600 m above sea level) of Czarnohora, the highest range of the Eastern Carpathian Mountains, on Petros and Hoverla (2058 m) peaks in the West, to the peak of Pop Ivan Czamohorski in the East (Figures 4-6). The species also grows sparsely in the Eastern Carpathian range of Svidovce (Bliznica peak), the Gorgon range (Sijniak and Chomjak peaks), Civciny, and the Marmorsk Alps (Pop Ivan Marmorski peak) (24). It grows on the steep mountain edges and faults creating thick and widespread thickets, but can also be found growing in small groups or individually. Often, it can be found growing on the highest peaks of the mountain (6, 7, 19, 24). Just below the tree line, it grows together with Pinus mugo Turra (Figure 7) (22). The plant likes to grow in places protected from winds, where a heavy blanket of snow accumulates (such as sharply arched folds, rock crevices, etc.) in stony sub-alpine and alpine meadows (Figure 8), and on rock slide paths. Although it often grows with various amounts of exposure to sunlight, the plant prefers sunny locations.

Rhododendron myrtifolium generally grows on skeletal, brown soils transitional between meadow soils and peats. On Czarnohora, it grows on surfacing sandstone, and in the Marmorsk Alps on gneiss and crystalline schist. Roots grow in the shallow surface of organic layers that cover the rock. The organic layer is highly acidic, with the pH ranging from 3.8-4.4. Some authors suggest that R. myrtifolium grows on limestone rocks (25, 15, 14). However, our observations agree with the former Soviet Union botanists (6, 24) who noted that R. myrtifolium , like Loiseleuria procumbens , a rare member of the Ericaceae in the area, develops a shallow root system with thin roots growing in the organic layer accumulated above the limestone rocks.

The observations of the Erica Polonica group while exploring the slopes of Polonina Pozyzevska, on June 10 and 11 in 1997, and reaching the peaks of Dancerz (1850 m) and Turkul (1932 m) support earlier reports. We came across the first group of Rhododendron myrtifolium at about 1200 m above sea level. These rhododendrons were growing among other species including Dentaria glandulosa W. K., Primula longiflora All., P. carpatica Fuss., Aposeris foetida (L.) Less., Alchemilla glabra Neygenfind, Anemone nemorosa L., Lycopodium selago L., Vaccinium vitis-idaea L., V. myrtillus L., Juniperus nana Willd., with mosses Hylocomium splendens (Hedw.) Br. eur., Pleurozium schreberi (Wi lid.) Mitten and Polytrichum juniperinum Willd. Also found close by were Tussilago farfara L., Mutellina purpurea (Poir) Thell. and Pulsatilla alpina (L.) Schrk. Growing between the low rhododendron shrubs we found Centiana asclepiadea L. (an interesting ornamental plant), Chrysosplenium alpinum Schur., Loiseleuria procumbens (L.) Desv. We first observed Loiseleuria , a low growing plant, on our way to the Hoverla summit. It has small leaves, red flowers that open in June/July, and stems that creep along the rocks. Loiseleuria procumbens grows only on limestone where its own decaying matter creates about a four-inch thick organic layer with a low pH (12). Where the humidity was higher, R. myrtifolium was seen with Caltha lutea Sch. N. K. and low shrubs of Juniperus communis L. Along the narrow paths of the steep hills, we saw continuous hedges of Alnus virdis (Chaix) D. C. with their characteristically bent stems that reminded us of a scythe. The rhododendrons were of various heights and grew rather loosely. Their flower buds were already swollen; however, only a few blooms were open (Figure 9). The rhododendrons with open blooms were more frequent at 1500 m above sea level and on shrubs growing in the full sun, surrounded by rocks (Figure 10). In the area between Polonina Pozyzevska and the peak of Dancerz more rhododendrons were bursting into flower, but in general it was just the beginning of the blooming season. Only later, probably at the end of June to early July, would the mountain shimmer with pink blossoms. Above the tree line, the rhododendrons were massed. Sometimes it was difficult to find a spot for one's foot in order not to step on the stems spreading between other shrubs on the shallow layer of soil and rocks. The stems self-rooted where they were adjacent to wet soil. Rhododendron myrtifolium appeared to be renewing itself also by self-seeding, especially with Pinus mugo close by. Pinus mugo may create the shade necessary for the seedlings' survival. The Erica Polonica Group members found the shrubs to be healthy, with no signs of past diseases or pest problems.

The number of natural stands of the rhododendron is diminishing. Botanists that examine the Carpathian flora blame the impact of humans on the reduction of the growing range of the species (M. Czekalski, personal communication). In fact, in the former Soviet Union R. myrtifolium was listed as an endangered species in the so-called "Red Book," that listed all endangered species in the country. Once the plant was listed in the book, it was prohibited by law to harvest, cut or destroy the plant. The former Soviet Union authorities recognized the value of R. myrtifolium , and included a part of the growing range of the species into a state-controlled sanctuary forest. Rhododendron myrtifolium was introduced into cultivation in 1846, five years before its description by Schott and Kotschy (1851), but today it is seldom cultivated. However, over the years several attempts have been made. In the former Soviet Union, it was first cultivated in St. Peterburg. It bloomed and produced fruit until 1959 and then perished. In 1964, a few young shrubs of R. myrtifolium were dug from natural stands from the Turkul Mountains in the Eastern Carpathian region and moved to the Central Botanical Garden in Moscow. They bloomed for the first time after ten to fifteen years of growing. The blooming period lasted from the second part of May to the beginning of June, and sometimes was repeated in August (3). In Moscow, the plants were cold hardy. They survived the harsh winter of 1978/79 where on Dec. 15, 1978, the temperature in Moscow was 1.6°C. Two days later the temperature dropped to -26°C during the day, and to -27°C at night. On Dec. 30, the temperature dropped further to -37°C (the minimum temperature on the ground surface on that day was -43°C with the soil frozen to a depth of 60 cm). The average snow cover in the first part of December was in the range of 5-8 cm and later increased to 11-13 cm. The following May and June, Moscow experienced a drought. However, July 1979 was cold and wet, which was helpful for the plant's survival. The weather in August was typical for the month and a second growth of tissue was observed (3). The average yearly temperature in Moscow is 3.8°C, minimum temperature is -42°C with average yearly rainfall of 587 mm. The number of frost free days is about 160 per year, and the average length of the vegetative period (determined by 5°C or above temperature) is about 92 days per year. In Moscow, R. myrtifolium did not bloom every year. In general the Moscow climate is not suitable for rhododendrons because of its cold winters with minimal snow accumulation along with dry summers. In spite of the plant's cold hardiness, it was not considered desirable in the area for massive plantings. It was only cultivated in the Botanical Gardens and Rock Gardens (2).

In 1964, Rhododendron myrtifolium was introduced to the Botanical Gardens in Kirovsk, Kiev, Lvov, and Uzgorod (Ukraine), Minsk (Belarus), Salaspils (Latvia), and Tallinn (Estonia). In Kirovsk, Lvov and Tallinn, the rhododendron bloomed and had fruit; in Kiev it did not bloom every year, and finally perished after a drought (1, 4, 5). Botianovskiy (8) wrote that R. myrtifolium was brought to Minsk in 1976 from the natural stands in the Carpathian Mountains (Czemiovce). In the 1960s, it was replanted from the natural stands of the Carpathian Mountains into the Botanical Garden in Latvia, again with no success. However, plantings brought from the Hoverla Mountain to the Riga Botanical Garden (Latvia) in 1975 and 1977 adapted well, and in 1980 quite a few shrubs bloomed and produced fruit.

In Poland, Rhododendron myrtifolium is found growing at the Botanical Garden in Wroclaw and at the Bolestraszyce Arboretum (21). In Great Britain, the plant survives temperatures to -21 °C and in the United States it can be grown in the USDA 6b-7a cold hardiness zone (9).

Although, as mentioned above, Rhododendron myrtifolium appears to renew itself in the wild by self-seeding under the canopy of Pinus mugo , its propagation from seeds is generally difficult. Seedlings grow very slowly and require extensive care. Propagation by cuttings or layering with auxin treatment have brought good results. The best rooting comes from two-year-old wood, but rooting and subsequent growth are slow (Czekalski, personal observations).

Rhododendron myrtifolium has some limitations, but also it has some very desirable characteristics, such as cold hardiness, attractive flowers and foliage, and low growth habit. We encourage the use of this plant in arboreta and breeding programs. Considering the cold hardiness resistance and the ornamental value, R. myrtifolium should find a permanent place in gardens not only in Europe, but possibly also in the United States.

¹ R. myrtifolium has since been placed in section Rhododendron , subsection Rhododendron (The Rhododendron Handbook 1998 , RHS).

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