Climate

The Scandinavian climate is very diverse and exciting. The great diversity concerning geography creates huge differences when it comes to temperature, precipitation, wind and hours of sunshine.
 

Climatologically differences in Scandinavia

It is mainly the coastal areas that are able to cultivate a range of palms successfully. The coast of western Norway (Egersund – Molde) comes out as the best place, because of the an annual winter temperature that lies above 0 °C. Parts of the Norwegian west coast can actually be classed up to USDA zone 8B and 9A.

The Norwegian coast further north to Bodø and Lofoten has also relative mild winters, but the growth season’s length and strength is very weak this fare north. Palms need warm days over a longer period to develop and build up the hardiness.

The winter temperatures along the western coast of Norway are mainly a result of favourable wind directions. The mildest weather occurs often when the winds come from a southwestern direction, because the air above the North Sea and the Atlantic Ocean is always mild. Easterly winds give mainly the lowest temperatures, since they have travelled from the cold continental areas in the east. The temperature in these areas drops fare down because there is no oceans to heat the air. But eastern winds can give foehn wind along western Norway, which of course is positive.

Along the southern coast of Norway and the western coast of Sweden (Lysekil - Helsingborg), the summers are warm and sunny. But unfortunately, these areas have winters that are often too cold for most of the palms mentioned on this Website. The annual winter temperatures lies, many places, under 0 °C. The minimum temperatures each winter falls so fare down that these areas can be classified as USDA zone 7A, perhaps 7B some places. But despite of cold winters, there is hope: Rhapidophyllum hystrix and Sabal minor should perform well in these areas, since they both manage cold winters, but need sunny summers to develop properly.

The marine parts of southwestern Sweden have milder winters than further north in the country. The annual winter temperatures lie approximately at 0 °C, and the minimum temperature goes rarely below -10 °C. This region has also warm summers. These favourable factors make southwestern Sweden a good place to grow a good range of palms. The lowest temperatures in Skåne occur mainly when the wind comes from the north, since there are no oceans in the north to heat the air. All other winds must pass an ocean, more or less. The marine areas of southwestern Sweden can be classified as USDA zone 7B or 8B.

The coast from Skåne to Stockholm is very cold during the winter, which will cause most palms to freeze down and die. The area belongs mainly to USDA zone 6B and 7A. Only the hardiest species could stand a chance. But out in the Baltic Sea, on the island of Gotland, the climate is much milder than on the mainland: USDA zone 7B, perhaps 8A. The eastern coast of Sweden is very exposed for cold winds from west, north and also from the east if the air over Finland, the Baltic and Russia is very cold.

The winters in Denmark are much of the same over the whole country, because of its geography and small size. But still, the western coast of Denmark is the mildest. A good variety of palms, like Trachycarpus and Chamaerops, should perform well in this area. The western coast of Denmark, is known for much wind, which makes T. wagnearius a better plant for the garden than T. fortunei. Bornholm is also a very interesting place for cultivation of exotic plants. The winters are mild on Bornholm, and the summers are warm and sunny.

Hardiness zones

USDA (United States Department of Agriculture) has divided USA into different hardiness zones. Which zone a place came under was calculated out of which the annual minimum temperature through the years had been on a certain place. The higher zone, the higher annual minimum temperature. The USDA zone system has today become a highly reckoned international concept.

Overview over the USDA zones 4 - 9.

NB! Do not look at zones as an absolute factor for which you can grow in your garden, since the local climate can vary within a small area. Another thing about hardiness zones is that they are only calculated out of a small range of factors, which could cause a zone 8 more favourable than a zone 9 in the long run. Factors as wind, precipitation, and hours of sunshine are also deciding how good your local climate is. Look at zones only as guidelines! The map below is only meant that way.

Links:

The meteorological institutes of Scandinavia:

Meteorologisk institutt (Norway)

Danmarks Meteorologiske Institut (DMI)

Sveriges meteorologiska och hydrologiska institut (SMHI)

Other: