Hi Mikko, welcome! Great to hear of Finnish people getting into perma culture. If you need nitrogen fixing flowers, lupines are everywhere in Finland, just collect the seeds or dig them out and replant them in your garden. If you want nitrogen fixing berries you could try gummi or autumn olive.
PFAF
If you need to break up the hard clay in your garden, maybe somebody could bring you a load of woodchips. It will help against drying out the soil in summer, as well as attract soil life, worms and fungi etc..The worms will work the decaying
wood slowly into the clay.
There must be some wild plants that can break through the clay with a strong pen shaped
root around where you live in the wild no doubt.
I know it sucks if you can't just buy what you want, but nature is a very generous friend. I've collected over 200 different kinds of plants in my small garden, which attracts a great amount of insect, which attracts birds, who drop seeds and droppings.
I hope this English
Permie who lives in Finland, forgot her name comes on. She can help with specific information.
I know some Finns are busy building a school for self sufficiency, a very unique
project, they have a course roundwoodbuilding this summer if i remember correctly.
english version of Omavaraopisto
There is a dutchman on Permies from the North busy trying to collect seeds from Northern countries, that can stand the cold, there was a Finnish
permaculture project that sends adapted seeds for a small amount, don't know if they're still around. They were on
facebook, they must have open days or give courses.
You're not alone and your country has great potential! Keep us posted and ask whatever you want!