tiistai 14. marraskuuta 2017

Sunshine in the north!

In English for a change!

A friend studied Finnish climate, comparing it to the rest of a Europe. I did some reading myself, and results are interesting. Data is from here (thanks Slaven for digging that up!)

First here is a chart of sunny hours in some European cities (same graph as in previous blog, except I added average from other cities than Helsinki):

To simplify things, here is the same with less cities:

Athens is the sunniest, Glasgow is the darkest city in the data. In the summertime Helsinki does very well. In the December and January Helsinki is the darkest city, and of course if we go even more north, there will be no sunlight at all during winter months.

Trees are more or less dormant in the winter, so who cares about winter months! Here is the same chart of only summer half of the year (I know in Southern Europe active growing period starts before April and ends after Septemper).

Thing look rather nice for Helsinki. To summarize, we have a long winter, but we also have very good but short summer. Last three summers have been cold and rainy, but I try to be positive here!

I believe above has some implications. Growth period starts at April, and autumn really starts at the end of August. If all goes well, we get 5 months of active growing period. Autumn is very long, dark and rainy. Often weather as about the same from September to Chrismas, just getting slowly cooler. There may be several short periods when temperatures are below zero.

It may sound strange, but I needed to see charts above to fully understand, that often we can not do things like they are done more south. For example,
  • How many growth spurts there are for deciduous trees
  • Can one repot in autumn, or to put it better, HOW can one repot in the autumn, to get full use of the long autumn and short summer (protection from both rain and coldest temperatures, even for domestic trees?)
  • April is already quite sunny, but there is still snow. How can we elongate growing period in the spring? Even to March?
  • August, the same thing. Domestic trees are starting to prepare for winter already, and they are wise to do that. Trees from south, they could still grow. Perhaps even to September?

3 kommenttia:

  1. This idea of yours about autumn repotting might be very useful for us here. When I repotted in spring one chinese elm it took a month or even more to see some growth, looked like it was repairing the damage/filling the pot with roots for so long. With our short seasons as you mentioned it might be really useful to have that reparation/filling roots process happening before spring so that trees can jump start faster in the growing season! I am looking forward for more data/theory/contemplation on this subject :)
    The post is in English so I also added comment in English :)

  2. Might it be fine to do with deciduous a little bit earlier than conifers before the leaves drop, perhaps September or maybe even earlier? We don't have heat stress in August so that is not the limit I assume. Conifers maybe beginning of October?

  3. Conifers are green, they should be just fine, if protected from rain? Deciduous, they should still have green working leaves? Deciduous, August, Conifers October? Sounds like a plan to me!


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