Purple asparagus

My green asparagus (now into their 5th year) have done incredibly well this year but the purple bed has been disappointing. I realised recently its location is far more exposed, as the green asparagus bed enjoys the shade of my neighbours' established quince tree in the height of summer, while the purple one is in full sun. 

However, since temperatures started cooling down, the purple crowns have produced new stems so the situation is not as bad as I feared.

I'm still considering planting new (male) purple crowns but I'll have to be careful where I plant them to avoid disturbing the roots of existing crowns.