Palms in Hungary

Growing palms in the city where the Buda meets the Pest. Familiar palms, familiar problems, familiar pleasures
Andras Nemenyi, 1118 Budapest, Menesi Ut 73, Hungary
Chamaerops No.29 Winter 1997

A fine collection in the conservatory at Elte Botanical Gardens, Budapest

Palms have been cultivated in Hungary as in most Central European countries since the Baroque. During the 19th century they have become favourites as potplants for interior decoration, their height of fame was at the turn of the century when new conservatories were built in Botanic Gardens, mansion parks and also glazed balconies, "winter gardens", as parts of city houses, became fashionable. Palms were available from growers in a large variety of species and sizes. An outstanding personality of the time, Archduke Joseph, was a keen palm collector. His neoclassical conservatory in Alcasút housed 77 species of palms in 1891 and he tried to introduce some 30 species outdoors in his palace park in former Fiume (Rijeka, Croatia) on the Adriatic coast. Nowadays the largest palm collection well worth seeing is the one in the conservatory of ELTE Botanical Gardens, Budapest. The collection of over 150 taxa includes specimens as Latania verschaffeltii, Arenga ambong, Guihaia argyrata, Copernicia fallaense, Coccothrinax species, Cocos nucifera cultivars: "King", "Maypan" etc.

Most people living in the mild western areas of Europe think Central Europe is too cold for the outdoor cultivation of palms which is true for most of the region. Hungary can be characterised as having a transitional climate between the maritime warm temperate climate of West Europe and the continental climate of East Europe. The annual precipitation is between 500-900 mm. and the hours of sunshine are 1700-2100. The mean monthly temperature for the coldest month, January, is 0 to -4deg. C and for the warmest, July, +19-22deg. C. The period with median daily (mean of min. and max. temp.) temperatures above +10deg. C range from the beginning of April until the end of October. On average, every 10 years there is a severe winter.

The limiting factors of outdoor palm cultivation for us here are the extent and duration of minimum temperatures each winter. The main factors influencing our local microclimates in order of importance are: 1) microtopography 2) level of urbanisation 3) position of the area within the country. Hungary is situated in a basin almost interlocked by mountain ranges, the Alps in the west and the horseshoe shaped Carpathians from the north to the south-east. Plains dominate the landscape to the east, south-east and hills and mountains to the north-east of the Danube. Here the mean extreme minimum temperature is between 17 and -20deg. C each winter and in the far northeast below -20deg. C. A mixture of plains, low hills and mountains dominate most of the area to the west of the Danube.

Mainly the west, south-west are milder areas where the lowest temperature in winter is -15 to I6deg. C on average. It is here where under favourable microclimates palms can be grown outdoors. 2) During winter in urban areas heat lost from buildings warms the adjacent air also buildings block the free movement of winds (reducing windchill factor). Thus the downtowns can be around +5 to +8deg. C warmer than the outskirts of cities and towns mainly during extreme cold weather. 1) Microtopography is an important factor in landlocked areas like Hungary, influencing the intensity of solar radiation and temperature. Land on slopes of hills and mountain sides with south exposition, in heights not over 300m altitude (a.s.l.) are warmer in spring, autumn and winter compared to adjacent valleys and plains. This is especially true during winter on slopes situated at altitudes half way between the valley floor and the mountain peak.

This is where the phenomenon "temperature inversion" occurs on those clear, still nights, during anticyclonic weather, when there is snow cover on the ground and heat is lost through drastic radiation. These are nights dreaded by all "northern palm enthusiasts" when the extreme low temperatures occur during winter. The cold air flows down the slopes and accumulates in the plains, valley floors, where it cools further while the warmer air layers lie on top of it. Thus the difference between the air temperature in the valley floor and the middle of the mountain slope can be around +4 6deg. C and in extreme cases +8-10deg. C. For example during the abnormally cold weather of January 1997 the minimum temperature was 22deg. C in the plains and only -13deg. C on the hill slope 100 meters higher in altitude (Tenkes Hill, Siklós-Máriagyúd, SW Hungary). Usually the colder the temperature cools in the plains the greater is the difference compared to the mountain side. This great temperature difference is only apparent under the above weather conditions.

When it is cloudy, radiating heat is not freely lost, so neither does the temperature in the valley floor cool down too much nor is there great difference compared to the mountainside, usually +12deg. C, which difference is typical under all weather conditions during the summer months. This means that on these mountain slopes the extreme minimum temperatures range between -8 and -14deg. C. The above topographical characteristics are typical of the historical wine growing regions along the hillsides of the Northern shores of Lake Balaton (Badacsony and Tihany), the slopes of the Mecsek and Villó nyi mountain ranges (above Pócs and Siklós-Máriagyúd, SW Hungary). Also the slopes in the SW part of Budapest offer similar conditions. In these regions figs (Ficus carica) have been grown in gardens for more than a century, also Capressus sempervirens and an occasional Musa basjoo can also be located.

The first experimental outdoor palm plantings were done by two dendrologists, Zsolt Debreczy and István Rácz in the late sixties. They are both recognised for their successful efforts in introducing and promoting various Mediterranean type exotic plant taxa (Cupressus, Albizzia, Melia, winter hardy Opuntia, Yucca species etc.) both in public plantings and among plant enthusiasts. My interest in palms led me to start collecting them from 1983 and to become a member of the IPS in 1985. Continuing where the two dendrologists left off, I have convinced some public gardens to plant outdoors some or more cold hardy palms since 1986. Over the years the most important thing I realised was that I should always consider what is best for my palms and that I have to accept reality. As I had no conservatory to grow my palms to perfection, I donated my collection of over 200 taxa to ELTE Botanical Gardens, Budapest in 1991. Since then I have focused my practical interest on growing the few cold hardy species in my garden in SW Hungary. The first palm species tried out-of-doors and the one which is most adaptable under our climate is Trachycarpus fortunei. Larger, between 1620 years old, 3-4m high flowering specimens of which can be seen in the ELTE Botanical Gardens, the Buda Arboretum of the University of Horticulture and Food Industry, the 'Varga Márton' Horticultural Secondary School in Budapest and the Botanical Garden of the University of Pécs. Young 34 year old plants produce 3-4, the 8-10 year old specimens grow 67, while the trunked 1618 year old palms produce 14-18 new leaves per year. Larger specimens from 0.75m trunk height will flower, and if both male and female plants are present, produce viable seeds each year.

Other species successfully growing in some public and private gardens include young specimens of Chamaerops humilis (the heart of which is very sensitive to precipitation during our winters), Rhapidophyllum hystrix, Sabal minor (flowering too late for its seeds to ripen), Trachycarpus wagnerianus T. takil Unfortunately Trachycarpus martianus (Khasia) defoliates when the first freeze of -5deg. occurs, so it is too tender for us here. I suspect the same will apply for T. martianus (Nepal) and even T. latisectus might not be hardy enough. Nannorrhops ritchiana (Iran seed origin) is not hardy (its roots easily rot and it grows very slowly).

Probably even specimens from more frost hardy provenance are more suited to a warmer climate, needing a longer growing season with higher temperatures than in Hungary. The heart of all the young palms need to be protected while still trunkless from the snow in our winters. When maximum daily temperatures range constantly below +5deg. C and there are several days with clear skies and sunshine during anticyclonic winter weather, palms like other evergreens suffer from "photochilling". This means leaves steadily turn yellow because cold stress is physiologically enhanced by irradiance. Thus winter protection by totally covering young plants of all species is beneficial not only in protecting from wind, but also from excess sunlight. Hopefully in the mildest microclimates palms, with proper care, will become not a rare sight in gardens with a southern touch.