Bio-indicative plants... a trial to understand them better (Anais, France)

However, i had a lot to learn... So i started to get back to the basis of plants growing needs (hopefully a full part is dedicated to this at the beginning of the book). After that, i tried to recognize, draw  and understand a couples of "weeds" and understand what they could tell me about the soil
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Why is only thistle growing here ? What is this plant i see all around the driving path ? What can it tell me about the farming soil ? 
After hearing about this guide for diagnostic of soil by analysing bio-indicative wild plants in an online course about plant recongnition, i decided to get the guide and see what i could learn about the farm soil.​

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