Sunlight: Finland versus Europe

Idea of my “research” was to compare the conditions to grow bonsai between Finland and the rest of Europe.

Potential of solar energy in Finland, the name tells it all.

2 pictures from the above title, giving reliable data:


Finish cities






Excerpt from above title:

The amount of solar energy is about the same in Finland as in Central Europe, but most of the radiation (1170 kWh/m² per year) is generated in the southern part of Finland during May to August. (VTT, 43, 2015) In Finland, there is more diffuse radiation than direct radiation. Diffuse radiation is more effecting, because in southern Finland half of the radiation is diffuse radiation. Diffuse radiation means that the sunlight has been scattered by molecules and particles at the atmosphere, but has still made it down to the surface of the earth. Solar irradiation is lower in northern Europe than in central or southern Europe. The average daily irradiation in Finland is about 900 kWh/m².

The same can be seen on the map of European solar irradiation. More data per country is also available.

Finland (south) is sunnier than Sweden/Norway, part of Be-Ne-Lux, UK and Ireland!

Average sunshine in Europe shows Helsinki compared to other cities, 1780 hours versus:

  • 1546 in Brussels/Belgium,
  • 1504 in Cologne/Germany
  • 1364 in Birmingham/UK

More accurate date per month to see when is the most light and how it compared with other months/cities can be done via solar calculator.

Not to loose the link to this interesting material:

The long days of a temperate-Arctic growing season provide an integrated fluence of photosynthetically active radiation (PAR, λ = 400–700 nm) similar to mid-latitudes (Jagels and Day 2004). Compared with mid-latitudes, however, the Arctic light regime provides irradiances below the photosynthetic saturation point of many tree species for a greater amount of time (higher proportion of “useful” radiation). In addition, irradiance in the Arctic lies for a greater proportion of time within the more linear portion of the photosynthetic light response curve, where photosynthetic efficiency (mol CO2 fixed per mol incident quanta) is maximized.


Graph of the sun light per city during the year shows the relation between the cities (Thanks Jani!):

Sunny hours

It is easilly visible that south of Finland is not at all having low level of sun light. All UK cities (from the available statistics) are below. It does show slightly narrower bell curve than some other cities but all of them are way more south.

My 5 cents
  • The lack of sun is not an excuse for not growing bonsai or to complain of slow/insufficient growth.
  • The slightly longer autumn is actually even better for plants to prepare for overwintering.
  • I have not noticed summer dormancy in my trees. They grow all the time during the summer. Maybe the speed slows down but to me not noticeably.

What does create difficulties over here is the severe winter. Nevertheless, with correct tools/structures that can be overcome. Any garden suffices, balconies are slightly bigger problem but not at all impossible!

So, only I can say is, take your tools and take the challenge 😀

Next: Relating monthly temperatures with the sun light.

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  1. Jani

    This is very important post! At summertime, we actually get more sun than those living more south?

    • tato

      Yes. We have longer days and less cloudy (whatever that means:D) spring/summer that it gathers more sunshine in a year.
      I have lived in north Germany for 2 years and I can confirm that many sunny days I haven’t experienced. The Netherlands and UK are stories of their own too. What surprised me was Belgium (considering how many bonsai nurseries they have and how well developed bonsai circles are) and to some extent Czech. Thought there is better situation.
      What is though worrying is climate change on our side. The latest years were not so sunny 🙁 Lets hope it is a temporary case.

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