Corydalis lutea
I make no apology for this. Some would consider this a weed. Around here it grows everywhere. The railway bridges seem to be a favourite place but it does not confine itself. It is true it seeds freely and turns up all over the place but, look at it..., how can you turn it away? Sometimes I pull it out, most times I just live with it. The foliage is delightful and the flowers bring a smile no matter what. The blue flower beyond is Geraniun nodosum, another wonderful plant that seeds freely.