C'est bien de persévérer. On apprend toujours de toutes les tentatives. Chez moi il fait encore froid le matin je les rentre le soir. Ces plantes ont besoin de beaucoup d'air. Bonne chance.
@MisterZ, thanks for your advice.
In fact, at the moment I too take the seedling indoors in the evening and shelter her in a small greenhouse during the day. If the weather continues like this and the seedling grows as she should, I think I will start to leave her outside at night too and remove the greenhouse at the beginning of May, when she will be more robust.
P.S.: I really like your profile picture. I love cats.