How do I protect a Buddleja colvilei in the winter?

I don't know if that's good news or bad news! Are they shy with flowers?

Interesting what you say about pruning because the flower I have is on growth which has appeared this year.

 

They tend not to flower after a hard winter. This is because the growing points that produce the new wood with flowers are formed the previous autumn. If new buds have to be formed in spring, these are less likely to bear flowers. This is why I recommend only tidying up the plant after flowering and never hard pruning in spring.

Once they are big and established, and with a mildish winter behind them, they can be free-flowering. One of mine has missed for two years because of hard frosts in 2022, but looks ready to flower well later on this August.

I have been trying to breed and select plants of Buddleja macrostachya that are a little hardier and more reliable.

 

OK. It has been granted a reprieve!

This is as good a time as any to thank you for your contributions here - they've really inspired me to explore Buddlejas. My garden is currently enjoying the extraordinary flowers of Buddleja davidii 'Dartmoor' - like Wisteria in late summer!

 

Many new flowers have appeared -- seemingly overnight!

 

@Howard Stone we have just been given a "Dartmoor" cutting from our neighbours. A really lovely specimen and in flower. Planted out yesterday so hopefully it will like its new home.